Two-gram is an ordered pair (i.e. string of length two) of capital Latin letters. For example, "AZ", "AA", "ZA" — three distinct two-grams.

You are given a string ss consisting of nn capital Latin letters. Your task is to find any two-gram contained in the given string as a substring (i.e. two consecutive characters of the string) maximal number of times. For example, for string ss = "BBAABBBA" the answer is two-gram "BB", which contained in ss three times. In other words, find any most frequent two-gram.

Note that occurrences of the two-gram can overlap with each other.

Input

The first line of the input contains integer number nn (2≤n≤1002≤n≤100) — the length of string ss. The second line of the input contains the string ss consisting of nn capital Latin letters.

Output

Print the only line containing exactly two capital Latin letters — any two-gram contained in the given string ss as a substring (i.e. two consecutive characters of the string) maximal number of times.

Examples
input
Copy 
7
ABACABA
output
Copy 
AB
input
Copy 
5
ZZZAA
output
Copy 
ZZ
Note

In the first example "BA" is also valid answer.

In the second example the only two-gram "ZZ" can be printed because it contained in the string "ZZZAA" two times.


#include<bits/stdc++.h>
using namespace std;
int main(){
	map<string,int> m;
	int n,mx=-1;
	cin>>n;
	string a,b,ans;
	cin>>a;
	for(int i=0;i<n;i++){
	    b=a.substr(i,2);    //每次从文本串取两位，
	    m[b]++;
	    if(m[b]>mx){       //保存数量最多的两位，的数量
		 mx=m[b];
		 ans=b;
	    }
    }
    cout<<ans<<endl;
	return 0;
}