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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
namespace agc006a
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            var s = Console.ReadLine();
            var t = Console.ReadLine();
            string[] st = new string[N+N];
            for(int i = 0; i < N; i++){
                st[i] = s[i].ToString();
                st[N+i] = t[i].ToString();
            }
            int count = 0;
            var hashset = new HashSet<string>();
            foreach(var str in st){
                if(hashset.Add(str)){
                    count++;
                }
            }
            
            Console.WriteLine(count);
        }
    }
}