Kr, Kb = map(int, input().split())
S = input()
ms = []

j = 0
for i in range(30):
    if S[i] == "W":
        ms.append(21)
    else:
        ms.append(j)
        j += 1

ma = 0
for i in range(2**20):
    T = ""
    ok = True
    for j in range(30):
        if i & (1 << ms[j]) == 0:
            T += S[j]
            if S[j] == "R" and len(T) > Kr and T[len(T) - Kr -1] == "R":
                ok = False
            if S[j] == "B" and len(T) > Kb and T[len(T) - Kb -1] == "B":
                ok = False                          

    if ok:
        ma = max(ma, len(T))

print(ma)