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study/Ref-docs/c_lib_guide/2.4.html
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study/Ref-docs/c_lib_guide/2.4.html
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<html>
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<head>
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<title>
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C Guide--2.4 float.h
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</title>
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<!-- Changed by: eric huss, 12-Mar-1997 -->
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</head>
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<body text="#000000" bgcolor="#FFFFFF">
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<center>
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<table border=0 width=100%>
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<tr>
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<td align=left width=20% valign=top>
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<a href="2.3.html">
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<img src="left.gif" border=0>
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Previous Section<br>
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2.3 errno.h</a></td>
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<td align=center width=60% valign=top>
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| <a href="index.html">Table of Contents</a> |
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<a href="index2.html">Index</a> |</td>
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<td align=right width=20% valign=top>
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<a href="2.5.html">
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Next Section
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<img src="right.gif" border=0><br>
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2.5 limits.h</a></td>
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</tr>
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</table>
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</center>
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<hr>
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<h1>2.4 float.h</h1>
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<p>
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The float header defines the minimum and maximum limits of floating-point number
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values.
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<p>
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<h2>2.4.1 Defined Values</h2>
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<p>
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A floating-point number is defined in the following manner:
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<blockquote>
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<i>sign value </i>E<i> exponent</i>
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</blockquote>
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Where <i>sign</i> is plus or minus, <i>value</i> is the value of the number, and <i>exponent</i> is the value
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of the exponent.
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<p>
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The following values are defined with the <code><b>#define</b></code> directive. These values are
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implementation-specific, but may not be any lower than what is given here. Note that in all
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instances <code><b>FLT</b></code> refers to type float, <code><b>DBL</b></code> refers to double, and <code><b>LDBL</b></code> refers to long double.
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<p>
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<table border=1>
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<tr>
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<td>
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<code><b>FLT_ROUNDS</b></code><br>
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</td>
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<td>
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Defines the way floating-point numbers are rounded.<br>
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<br>
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<table border=0>
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<tr>
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<td><code><b>-1</b></code></td><td> indeterminable</td></tr>
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<tr>
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<td><code><b>0</b></code></td><td> toward zero</td></tr>
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<tr>
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<td><code><b>1</b></code></td><td> to nearest</td></tr>
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<tr>
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<td><code><b>2</b></code></td><td> toward positive infinity</td></tr>
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<tr>
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<td><code><b>3</b></code></td><td> toward negative infinity</td></tr>
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</table>
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</td>
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</tr>
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<tr>
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<td>
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<code><b>FLT_RADIX 2</b></code><br>
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</td>
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<td>
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Defines the base (radix) representation of the exponent (i.e. base-2 is binary, base-10 is
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the normal decimal representation, base-16 is Hex).
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_MANT_DIG<br>
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DBL_MANT_DIG<br>
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LDBL_MANT_DIG<br>
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</b></code>
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</td>
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<td>
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Defines the number of digits in the number (in the <code><b>FLT_RADIX</b></code> base).
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_DIG 6<br>
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DBL_DIG 10<br>
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LDBL_DIG 10<br>
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</b></code>
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</td>
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<td>
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The maximum number decimal digits (base-10) that can be represented without change
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after rounding.
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_MIN_EXP<br>
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DBL_MIN_EXP<br>
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LDBL_MIN_EXP<br>
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</b></code>
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</td>
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<td>
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The minimum negative integer value for an exponent in base FLT_RADIX.
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_MIN_10_EXP -37<br>
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DBL_MIN_10_EXP -37<br>
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LDBL_MIN_10_EXP -37<br>
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</b></code>
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</td>
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<td>
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The minimum negative integer value for an exponent in base 10.
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_MAX_EXP<br>
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DBL_MAX_EXP<br>
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LDBL_MAX_EXP<br>
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</b></code>
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</td>
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<td>
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The maximum integer value for an exponent in base FLT_RADIX.
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_MAX_10_EXP +37<br>
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DBL_MAX_10_EXP +37<br>
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LDBL_MAX_10_EXP +37<br>
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</b></code>
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</td>
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<td>
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The maximum integer value for an exponent in base 10.
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_MAX 1E+37<br>
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DBL_MAX 1E+37<br>
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LDBL_MAX 1E+37<br>
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</b></code>
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</td><td>
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Maximum finite floating-point value.
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_EPSILON 1E-5<br>
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DBL_EPSILON 1E-9<br>
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LDBL_EPSILON 1E-9<br>
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</b></code>
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</td>
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<td>
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Least significant digit representable.
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</td>
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</tr>
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<tr>
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<td>
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<code><b>
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FLT_MIN 1E-37<br>
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DBL_MIN 1E-37<br>
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LDBL_MIN 1E-37<br>
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</b></code>
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</td>
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<td>
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Minimum floating-point value.
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</td>
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</tr>
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</table>
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<hr>
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<center>
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<table border=0 width=100%>
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<tr>
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<td align=left width=20% valign=top>
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<a href="2.3.html">
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||||
<img src="left.gif" border=0>
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Previous Section<br>
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2.3 errno.h</a></td>
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||||
<td align=center width=60% valign=top>
|
||||
| <a href="index.html">Table of Contents</a> |
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||||
<a href="index2.html">Index</a> |</td>
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<td align=right width=20% valign=top>
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<a href="2.5.html">
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Next Section
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<img src="right.gif" border=0><br>
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2.5 limits.h</a></td>
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</tr>
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</table>
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</center>
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</body>
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||||
</html>
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