Two-gram (thinking)

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 s

consisting of n 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 s = " BBAABBBA " the answer is two-gram " BB ", which contained in s

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 n

( 2≤n≤100 ) — the length of string s . The second line of the input contains the string s consisting of n

capital Latin letters.

Output

Print the only line containing exactly two capital Latin letters — any two-gram contained in the given string s

as a substring (i.e. two consecutive characters of the string) maximal number of times.

Examples

Input

7
Flats

Output

AWAY

Input

5
ZZZAA

Output

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.

The meaning of the question: Find the substring of the two-gram with the most occurrences. A two-gram string refers to two consecutive letters that appear in the original string.

Idea: Open a two-dimensional array dp[x][y] to represent the number of occurrences of the two-gram string composed of str[x]str[y]

Code:

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
int dp[30][30];
int main(){
    int n;
    string str;
    cin>>n>>str;
    for(int i=0;i<n-1;i++){
    	int x=str[i]-'A';
    	int y=str[i+1]-'A';
    	dp[x][y]++;
	}
	int maxt=0,Last=0,Next=0;
	for(int i=0;i<26;i++)
	for(int j=0;j<26;j++){
		if(maxt<dp[i][j]){
			Last=i;
			Next=j;
			maxt=dp[i][j];
		}
	}
	printf("%c%c\n",Last+'A',Next+'A');
	return 0;
}