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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <stdio.h>

int solve(int N, char s[]) {
    if (N & 1) return 0;
    int flg = 0, n = N / 2;
    for (int i = 0; i < n; i++) {
        flg += s[i] != s[i + n];
    }
    return !flg;
}

int main() {
    int N;
    char s[101];
    scanf("%d", &N);
    scanf("%s", s);

    if ((N & 1) == 1) {
        printf("NO\n");
    } else { 
        int flg = 0, n = N / 2;
        for (int i = 0; i < n; i++) {
            if (s[i] != s[i + n]) {
                printf("NO\n");
                return 0;
            }
        }
        printf("YES\n");
    }

    return 0;
}