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>
#include <stdlib.h>
#include <string.h>

int main(){
  int N;
  scanf("%d",&N);
  
  if(N==1){
    printf("No");
    return 0;
  }
  
  char S[N];
  for(int i=0; i<=N; i++){
    scanf("%c",&S[i]);
  }
  
   int roop = N/2;
  
  int flag = 0; //1でNo
  for(int i= 1; i<=roop;i++){
    if(S[i] != S[i + roop]) flag = 1;
  }
 if(flag == 0){
   printf("Yes");
 }else{
   printf("No");
 }
}