Description

Given a string, find the first character that appears consecutively at least k times in the string.

Input Format

The first line contains a positive integer k, indicating the minimum number of consecutive occurrences required. (1 ≤ k ≤ 1000).
The second line contains the string to be searched. The string length is between 1 and 2500, and it does not contain any whitespace characters.

Output Format

If a character exists that appears consecutively at least k times, output that character; otherwise, output "No".

3
abcccaaab

c