from collections import defaultdict

def transformString(S):
    counter = defaultdict(lambda : 0)
    max_consecutive_count = 0

    for i in range(len(S)):
        if i == 0 or S[i] != S[i-1]:
            if S[i] == 'C':
                counter[S[i]] += 1
            else:
                max_consecutive_count = max(max_consecutive_count,counter[S[i]])
                counter[S[i]] += 1

        elif S[i] == 'C':
            counter[S[i]] += 1
        elif S[i] == 'T':
            counter[S[i]] += 1
            if counter[S[i]] == 0:
                max_consecutive_count = max(max_consecutive_count,counter[S[i]])

    return max_consecutive_count
N = int(input())
s = input()
print(transformString(s))