import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
import itertools

S = read().rstrip().decode()
ques = S.count('?')


def solve(a, b, c, d, e):
    stack = ['I'] * e + ['O'] * d + ['R'] * c + ['U'] * b + ['K'] * a
    K = 0
    KU = 0
    KUR = 0
    KURO = 0
    KUROI = 0
    for i, x in enumerate(S):
        if x == '?':
            x = stack.pop()
        if x == 'K':
            K += 1
        elif x == 'U' and K:
            K -= 1
            KU += 1
        elif x == 'R' and KU:
            KU -= 1
            KUR += 1
        elif x == 'O' and KUR:
            KUR -= 1
            KURO += 1
        elif x == 'I' and KURO:
            KURO -= 1
            KUROI += 1
    return KUROI


answer = 0
for a, b, c, d in itertools.product(range(21), repeat=4):
    e = ques - (a + b + c + d)
    if e < 0:
        continue
    x = solve(a, b, c, d, e)
    if answer < x:
        answer = x
print(answer)