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>
#define rep(i,n) for(int i=0;i<(n);++i)
using namespace std;
typedef long long ll;
int main(){
	int n,flag=0;
	cin >> n ;
	if (n > 1) {
		string s;
		cin >> s;
		for (int i = 0; i <(n / 2);i++) {
			if (s.at(i) != s.at(n / 2 + i)) {
				flag = 1;
				break;
			}
		}
	}
	else {
		char s;
		cin >> s;
		flag == 1;
	}

	if (flag == 0)
		cout << "Yes" << endl;
	else
		cout << "No" << endl;

	}