kr, kb = map(int, input().split())
s = input()
ans = 0
for br in range(1 << 10):
    for bb in range(1 << 10):
        t = []
        nxtr = 0
        nxtb = 0
        for c in s:
            if c == "W":
                t.append(c)
            elif c == "R":
                if br >> nxtr & 1:
                    t.append(c)
                nxtr += 1
            else:
                if bb >> nxtb & 1:
                    t.append(c)
                nxtb += 1
        l = len(t)
        ok = True
        for i in range(l):
            if t[i] == "R":
                if i + kr < l and t[i + kr] == "R":
                    ok = False
                    break
            elif t[i] == "B":
                if i + kb < l and t[i + kb] == "B":
                    ok = False
                    break
        if ok:
            ans = max(ans, l)
print(ans)