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
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.

Difficulty: introductory

Starter code:

Solutions:
n = int(input())
s = input()
a = [[0] * 26 for _ in range(26)]
for i in range(n -1):
    a[ord(s[i]) - ord('A')][ord(s[i + 1]) - ord('A')] += 1

mx = -1

for i in range(26):
    for j in range(26):
        if a[i][j] > mx:
            mx = a[i][j]
            ans = chr(i + ord('A')) + chr(j + ord('A'))

print(ans)