import sys

sys.setrecursionlimit(10 ** 6)
def MI(): return map(int, sys.stdin.readline().split())

def ok(bit):
    a = []
    for i, c in enumerate(s):
        if c == "R":
            if bit & 1:
                if len(a) >= kr and a[-kr] == 1: return False
                a.append(1)
            bit >>= 1
        elif c == "B":
            if bit & 1:
                if len(a) >= kb and a[-kb] == 2: return False
                a.append(2)
            bit >>= 1
        else:
            a.append(0)
    return True

def main():
    popcut = lambda x: bin(x).count("1")
    ans = 0
    # 1がたっている所を残す
    for bit in range(1 << 20):
        p = popcut(bit)
        if p <= ans: continue
        if ok(bit): ans = p
    print(ans+10)

kr, kb = MI()
s = input()
main()