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

int main(void)
{
    int n;
    scanf("%d",&n);
    char str[100];
    scanf("%s",str);
    int i,j;
    char str1[100]="",str2[100]="";
    if(n%2!=0)
    {
        printf("NO");
        return 0;
    }

    else
    {
        for(i=0;i<(n/2);i++)
        {
            str1[i]=str[i];
        }

        for(i,j=0;i<n;i++,j++)
        {
            str2[j]=str[i];
        }
    }

    if(strcmp(str1,str2)==0)
        printf("YES");
    else
        printf("NO");

    return 0;
}