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(void){
  int n,a[300]={0},i,count=0;
 scanf("%d",&n);
 char s[n];
 scanf("%s",s);
 for(i=0;i<n;i++)
 {
  a[s[i]]++;
 }
  for(i=0;i<300;i++)
  {
  if(a[i] == 2)
    count++;
  }
  if(n%2 == 1)
    printf("No\n");
  else{
  if(count == n/2 || count%2 == 0)
    printf("Yes\n");
  else 
    printf("No\n");
}
return 0;
}