#!/usr/bin/ python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
import itertools


KR, KB = map(int, readline().split())
S = read().rstrip().decode()
ind = [i for i, x in enumerate(S) if x in 'RB']


def test(ind):
    se = sum(1 << i for i in ind)
    T = [x for i, x in enumerate(S) if not ((se >> i) & 1)]
    if any(x == y == 'R' for x, y in zip(T, T[KR:])):
        return False
    if any(x == y == 'B' for x, y in zip(T, T[KB:])):
        return False
    return True


def solve():
    for remove_size in range(21):
        for remove_ind in itertools.combinations(ind, remove_size):
            if test(remove_ind):
                return 30 - remove_size


print(solve())