from sys import setrecursionlimit
setrecursionlimit(10**6)
def Check(S):
    if S in dic:
        return dic[S]
    N = len(S)
    flg = True
    for i in range(N):
        if S[i] == 'R':
            if 0 <= i - Kr and S[i-Kr] == 'R':
                flg = False
            if i + Kr < N and S[i+Kr] == 'R':
                flg = False
        if S[i] == 'B':
            if 0 <= i - Kb and S[i-Kb] == 'B':
                flg = False
            if i + Kb < N and S[i+Kb] == 'B':
                flg = False
    if flg:
        dic[S] = N
        return N
    ret = 0
    for i in range(N):
        if S[i] != 'W':
            T = S[:i] + S[i+1:]
            ret = max(ret, Check(T))
    dic[S] = ret
    return ret

Kr,Kb = map(int,input().split())
S = input()
dic = {}
print(Check(S))