<?php

define('HELLO', 'nyanpass');
define ('NOT_HELLO', '-');

$n = (integer)trim(fgets(STDIN));
$lists = array();
$tmp_list = explode(' ', (string)trim(fgets(STDIN)));
foreach ($tmp_list as $key=>$val) {
    if ($val === HELLO || $val === NOT_HELLO) $lists[] = $key;
}
for ($i = 1; $i < $n; $i++) {
    $tmp_list = explode(' ', (string)trim(fgets(STDIN)));

    for ($j = count($lists)-1; $j >= 0; $j--) {
        if ($tmp_list[$lists[$j]] !== HELLO && $tmp_list[$lists[$j]] !== NOT_HELLO) {
            unset($lists[$j]);
        }
    }
    $lists = array_values($lists);
}
echo count($lists) === 1 ? $lists[0]+1 : '-1';
?>