977_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 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
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.
```python
n = int(input())
k = str(input()) 
Max = 0
for i in range(n-1):
    t=k[i]+k[i+1]
    z=0
    for j in range(0,n-1):
        s=k[j]+k[j+1]
        if (s==t):
            z=z+1
    #print(z)
    if (z>Max):
        Max=z
        res=t
print(res)

```