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,k,i;
  char s[100];
  scanf("%d",&n);
  scanf("%s",&s);
  k=0;
  if((n%2)!=0)k++;
  else if(n==0)k++;
  else
  {
    for(i=0;i<=(n/2);i++)
    {
      if(s[i]!=s[(n/2)+i])k++;
    }
  }
  if(k>0)printf("no");
  else if(k==0) printf("yes");
  return 0;
}