<?php
$_fp = fopen("php://stdin", "r");
`$v=fgets($`_fp);
`$n=fgets($`_fp);
`$a=fgets($`_fp);
`$ar=split(" ",$`a);
sort($ar);
for(`$i=0;$`i<`$n;$`i++){
 if (`$v==$`ar[`$i]){$`num=$i;};}
print $num;
fclose($_fp);
?>

output says no response but when i change like this

if (4==`$ar[$`i]){`$num=$`i;};}

then it returns value of $i.. (test case0)

what is the problem???