KR,KB = list(map(int, input().split(' ')))
S = input()

def meet(s):
    yes = True
    length = len(s)
    for i in range(len(s)):
        if s[i] == 'R':
            if (i+KR < length and s[i+KR] == 'R') or (0 <= i-KR and s[i-KR] == 'R'):
                yes = False
        elif s[i] == 'B':
            if (i+KB < length and s[i+KB] == 'R') or (0 <= i-KB and s[i-KB] == 'B'):
                yes = False
    return yes

def solve(m,s):
    if meet(s):
        return len(s)

    for i in range(len(s)):
        if s[i] == 'R' or s[i] == 'B':
            return max(m, solve(m, s[:i] + s[i+1:]))

print(solve(-1,S))