s = 'ZXZXZXXZXZXZXZXXZXZAAAAAAAAAAAAA'
f = [0] * len(s)
for i in range(2, len(s)):
    if s[i-1] + s[i] == 'ZX' or s[i-1] + s[i] == 'ZY':
        f[i] = f[i-2] + 1
    else:
        f[i] = 0
print(max(f))