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

The first line of input contains a positive integer k, indicating the number of consecutive occurrences. 1 <= k <= 1000. The second line contains the given string. The string length is between 1 and 1000 and does not contain any space.

Outputs the character if there is a character that appears at least k consecutive times; otherwise, outputs No.