Longest Contiguous 'A' Substring

Given a string S composed solely of uppercase English letters, your task is to determine the length of the longest contiguous substring that consists entirely of the letter A.

Formally, if there exists an index i such that the substring S[i...i+k-1] is composed of exactly k consecutive A's, you need to find the maximum possible k.

Note: The input string is guaranteed to contain only uppercase letters.

inputFormat

The input consists of a single line containing a string S, where S is formed only by uppercase English letters.

outputFormat

Output a single integer representing the length of the longest contiguous substring of A in the input string.

BAAAB

3