Problem:
Score : 200 points

Problem Statement

Snuke is interested in strings that satisfy the following conditions:

The length of the string is at least N.

The first N characters equal to the string s.

The last N characters equal to the string t.

Find the length of the shortest string that satisfies the conditions.

Constraints

1≤N≤100

The lengths of s and t are both N.

s and t consist of lowercase English letters.

Input

The input is given from Standard Input in the following format:

N
s
t

Output

Print the length of the shortest string that satisfies the conditions.

Sample Input 1

3
abc
cde

Sample Output 1

5

The shortest string is abcde.

Sample Input 2

1
a
z

Sample Output 2

2

The shortest string is az.

Sample Input 3

4
expr
expr

Sample Output 3

4

The shortest string is expr.

Solution in PHP (5.6.30) (judge verdict: Wrong Answer)

<?php
error_reporting(0);
$stdin = file_get_contents('php://stdin');
$line = explode("\n",$stdin);
$fi = 0;
$cnt = 0;
$list = array();
$key = new stdclass();
foreach($line as $l) {
  if (strlen($l)==0) continue;
  if ($fi == 0) {
    $a = explode(" ",$l);
    $key->A = $a;
    $fi++;
    continue;
  }
  if ($fi > 0) {
    $a = explode(" ",$l);
    $key->A[] = $a[0];
  }
}
$l1 = strlen($key->A[1]);
$l2 = strlen($key->A[2]);
if ($key->A[1]==$key->A[2]) {
  printf("%d\n",$key->A[0]);
  exit;
}
$len = $key->A[0]*2;
for($i=0;$i<$key->A[0];$i++) {
  if ($key->A[1][$key->A[0]-$i-1]==$key->A[2][$i]) {
    $len-=1;
  }
}
printf("%d\n",$len);