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

ms = [0] * 31
j = 0

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

ma = 0
for i in range(1 << 20):
    T = ''
    ok = 1
    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 = 0
            if S[j] == 'B' and len(T) > Kb and T[len(T) - Kb - 1] == 'B':
                ok = 0
    if ok:
        ma = max(ma, len(T))

print(ma)