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 <string.h>

int substr(char *t,const char *s,int pos,int len){
    if(pos < 0||len < 0||len > strlen(s))
        return -1;
    for(s += pos;*s!='\0' && len>0;len--)
        *t++ = *s++;
    *t = '\0';
    return 0;
}


int main(void) {
    int  N;
    char S[128];
    char S1[128];
    char S2[128];

    scanf("%d",&N);
    scanf("%s",&S);

    if(N%2 == 0){
		substr(S1,S,0,N/2);
        substr(S2,S,N/2,N/2);

        if(strcmp(S1,S2)==0){
            printf("Yes");
        }
      	
      	else{
          	printf("No");
        }
    }

    else{
        printf("No");
    }

    return 0;
}