B. Two-gram

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

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 $n$ ($2\le n\le 100$) — 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

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.

解题说明：此题的意思是统计字符串中出现AB AA BA类型的子字符串中出现次数最多的是哪个，遍历查找即可。

#include<cstdio>
#include<iostream>
#include<string>
#include<cstring>
#include<cmath>
using namespace std;

#define N	100

int main() 
{
	static char cc[N];
	static int kk[676];
	int n, i, max, amax;
	scanf("%d", &n);
	scanf("%s", cc);
	max = 0;
	amax = 0;
	for (i = 1; i < n; i++) 
	{
		int a = (cc[i - 1] - 'A') * 26 + (cc[i] - 'A');
		if (max < ++kk[a])
		{
			max = kk[a];
			amax = a;
		}
	}
	printf("%c%c\n", amax / 26 + 'A', amax % 26 + 'A');
	return 0;
}