Score : 200 points
You are given a string S consisting of uppercase English letters. Find the length of the longest ACGT string that is a substring (see Notes) of S.
Here, a ACGT string is a string that contains no characters other than A, C, G and T.
A substring of a string T is a string obtained by removing zero or more characters from the beginning and the end of T.
For example, the substrings of ATCODER include TCO, AT, CODER, ATCODER and (the empty string), but not AC.
Input is given from Standard Input in the following format:
S
Print the length of the longest ACGT string that is a substring of S.
ATCODER
3
Among the ACGT strings that are substrings of ATCODER, the longest one is ATC.
HATAGAYA
5
Among the ACGT strings that are substrings of HATAGAYA, the longest one is ATAGA.
SHINJUKU
0
Among the ACGT strings that are substrings of SHINJUKU, the longest one is (the empty string).