Undefined variable don't know why

[Tekron-X]

I am getting Undefind variables on lines 10 and 13 and not sure why.

<?php
$Count = 2;
do
{
    $Remainder = $_Post['Guess'] % $Count;
    $Count = $Count + 1;
} while ($Remainder != 0 && $Count < $_Post['Guess']);
if (($Count < $_Post['Guess']) || ($_Post['Guess'] == 0))
{
    echo ("Your number is not prime!");
}else{
      echo ("Your number is prime!");
}
?>

[Tekron-X]

Nevermind I figured it out It should be

$_POST['Guess']