import math
mmi, mma = math.inf, max
bls, brs = lambda x, y: x << y, lambda x, y: x >> y
kr, kb = map(int, input().split())
s = input()
red, blue = [], []
t = {}
use = {}
for i in range(1, 31):
    use[i] = True
    t[i] = s[i - 1]
    if t[i] == "R":
        red.append(i)
    elif t[i] == "B":
        blue.append(i)
ret = 10
tot = bls(1, 20)
for i in range(tot):
    ti = i
    for j in range(1, 11):
        tgt = red[j - 1]
        use[tgt] = ti % 2 == 1
        ti = brs(ti, 1)
    for j in range(1, 11):
        tgt = blue[j - 1]
        use[tgt] = ti % 2 == 1
        ti = brs(ti, 1)
    w = []
    for j in range(1, 31):
        if use[j]:
            w.append(t[j])
    valid = True
    for j in range(1, len(w) - kr + 1):
        if w[j - 1] == "R" and w[j + kr - 1] == "R":
            valid = False
            break
    for j in range(1, len(w) - kb + 1):
        if w[j - 1] == "B" and w[j + kb - 1] == "B":
            valid = False
            break
    if valid:
        ret = mma(ret, len(w))
print(ret)