codechef problem

kthElement.php

<?php

// problem
// Alice adds the numbers to list in the following order 
// [1,4,7,10,2,5,8,3,6,9]
// The 7th number in the list is 8

// solution

$b=[1,4,7,10,2,5,8,3,6,9];

$n = intval(trim(fgets(STDIN)));
$arr_temp = rtrim(fgets(STDIN));
$arr = array_map('intval', preg_split('/ /', $arr_temp, -1, PREG_SPLIT_NO_EMPTY));

$c=count($arr)-1;

$a=0;

if($c<count($b)) {
  $d=$arr[$c]-1;
  $a=$b[$d];  
}

echo $a;
// 8

//
// ashumeow
//

?>