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;

int main() {
  int N;
  string S;
  cin >> N;
  cin >> S;
  string ans = "No";
  
  if (N == 1) {
    ans = "No";
  }
  else if (N%2 == 0) {
    int M = N/2;
    if (S.substr(0,M) == S.substr(M,M)) ans = "Yes";
  }
  else {
    int M = (N-1)/2;
    if (S.substr(0,M) == S.substr(M+1,M)) ans = "Yes";
  }
  
  cout << ans << endl;
  
}