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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<iostream>
using namespace std;
bool concat(char* a,int n){
if(n%2==0){
int i=0;
int j=(i+n-1)/2;
while(i<j && j<n){
if(a[i]!=a[j]){
return false;
break;
}
i++;
j++;
}
return true;
}
else
return false;
}
int main(){
int n;
char a[100];
cin>>n;
for(int i=0;i<n;i++){
cin>>a[i];
}
bool s=concat(a,n);
if(s){
cout<<"Yes";
}
else{
cout<<"No";
}
}