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>
#include<stdlib.h>
#include<string.h>
#include<math.h>
 
#define num_max(p,q)((p)>(q)?(p):(q))
#define num_min(p,q)((p)<(q)?(p):(q))
int cmp(const void *a, const void *b)
{
	return *(int*)a - *(int*)b;//昇順
	 //降順ならreturn *(int*)b - *(int*)a;
}
int main()
{
	int n;
	char s[110];
	
	scanf("%d", &n);
	for (int i = 0;i <= n;i++)scanf("%c", &s[i]);
	if (n % 2 != 0) {
		printf("No\n");return 0;
	}
	int m = n / 2;
	for (int i = 1;i <= m;i++)
	{
		if (s[i] != s[i + m])
		{
			printf("No\n");
			return 0;
		}
	}
	printf("Yes\n");
	return 0;
}