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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main() 
{
	int n;
	scanf("%d", &n);
  	char s[n];
  	scanf("%s", s);
  	if (n & 1) 
  	    printf("NO");
  	else {
  	    int a = n / 2;
  	    for (int i = 0, j = a; i < a, j < n; i++, j++) 
  	        if (s[i] != s[j]) {
  	            printf("NO");
  	            return 0;
  	        } 
  	    printf("YES");
  	}
    return 0;
}