r, b = map(int, input().split())
S = input()

ans = 10

for bit in range(1 << 20):
    i = 0
    use = []
    for s in S:
        if s == "W":
            use.append(s)
            continue
        if (bit >> i) & 1:
            use.append(s)
        i += 1

    ok = True
    for i, s in enumerate(use):
        if s == "R" and i + r < len(use) and use[i + r] == "R":
            ok = False
            break
        elif s == "B" and i + b < len(use) and use[i + b] == "B":
            ok = False
            break
    if ok and len(use) > ans:
        ans = len(use)

print(ans)