B - Two-gram

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. You

#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<string>
#include<math.h>
#include<iostream>
using namespace std;
int main()
{
    int n,i,j;string s;
    scanf("%d",&n);
    getchar();
    cin>>s;
    int dp[100][100]={0};   ///利用二维数组来做；
    for(i=0;i<n-1;i++)
    {
        int x=s[i]-'A';
        int y=s[i+1]-'A';
        dp[x][y]++;     ///利用dp[x][y]，看谁出现的次数多，就值要大。
    }
    int mat=0,last=0,next=0;
    for(i=0;i<26;i++)
    {
        for(j=0;j<26;j++)
        {
            if(mat<dp[i][j])
            {
                last=i;next=j;
                mat=dp[i][j];
            }
        }
    }
    printf("%c%c",last+'A',next+'A');
}

解题思路：由于可以迭代去看，然后我们就用一个二维数组来保存那两个连续出现的字母出现的次数。至于用二维数组的那两个下标代表什么？就是代表那两个连续的字母

 

 

r 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

7
ABACABA

Output

AB

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.