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).