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: Accepted)

#include<stdio.h>
#include<math.h>

int main(){
  int N; 
  scanf("%d",&N);
  char str[N];
  scanf("%s",&str);
  
  int cnt = 0;
  if(N % 2 == 1){
    printf("No");
    cnt = 1;  
  }
  else{
  	for(int i = 0;i < N/2 ; i++){
  	  if(strncmp(&str[i],&str[i+N/2],1)!=0){
			printf("No");
        	cnt = 1;
       		break;
  	   } 
     }
  }
  if(cnt != 1)
	  printf("Yes");

  return 0;
}