Problem:
Score : 200 points

Problem Statement

Given are a positive integer N and a string S of length N consisting of lowercase English letters.

Determine whether the string is a concatenation of two copies of some string.
That is, determine whether there is a string T such that S = T + T.

Constraints

1 \leq N \leq 100

S consists of lowercase English letters.

|S| = N

Input

Input is given from Standard Input in the following format:

N
S

Output

If S is a concatenation of two copies of some string, print Yes; otherwise, print No.

Sample Input 1

6
abcabc

Sample Output 1

Yes

Let T = abc, and S = T + T.

Sample Input 2

6
abcadc

Sample Output 2

No

Sample Input 3

1
z

Sample Output 3

No

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll gcd(ll a, ll b) {
	if(a==0||b==0) return 0;
	if(a<b) swap(a,b);
	ll tmp = a%b;
	while(tmp!=0) {
		a = b;
		b = tmp;
		tmp = a%b;
	}
	return b;
}

int main() {
	int N; cin >> N;
	string S; cin >> S;
	if(S.substr(0,N/2)==S.substr(N/2,N/2)) cout << "Yes" << endl;
	else cout << "No" << endl;
}