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

def check(L):
    m = len(L)
    for i in range(m):
        if L[i] == 0:
            ni = i + r
            if ni < m:
                if L[ni] == 0:
                    return False
        elif L[i] == 1:
            ni = i + b
            if ni < m:
                if L[ni] == 1:
                    return False
    return True

ans = 0
for rbit in range(1 << 10):
    for bbit in range(1 << 10):
        L = []
        ri, bi = 0, 0
        for i in range(30):
            if S[i] == 'R':
                if (rbit >> ri) & 1:
                    L.append(0)
                ri += 1
            elif S[i] == 'B':
                if (bbit >> bi) & 1:
                    L.append(1)
                bi += 1
            else:
                L.append(2)
        if check(L):
            ans = max(ans, len(L))
print(ans)