file = open('17.txt')
s = file.readline()
f = [0] * len(s)
for i in range(2, len(s)):
    if (s[i] == 'A' and s[i-2] == 'A') or (s[i] == 'C' and s[i-2] == 'C'):
        f[i] = f[i-2] + 2
print(max(f))