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>

int main()
{
  int ret, i, N, ng_flag;
  char S[101];
  
  ret = scanf("%d", &N);
  ret = scanf("%s", S);
  if ( (N % 2) != 0 ) {
    printf("No\n");
    return 0;
  }
  
  ret = N/2;
  ng_flag = 0;
  for ( i=0; i<ret;i++ ) {
    if ( S[i] != S[ret+i] ) {
      i = ret;
      ng_flag = 1;
    }
  }
  if ( ng_flag )
    printf( "No\n" );
  else
    printf( "Yes\n" );
}