import copy

Kr, Kb = map(int, input().split())
S = list(input())

br = []
for i in range(len(S)):
    if S[i] == 'B' or S[i] == 'R':
        br.append(i)

ans = 0
for i in range(2 ** len(br)):
    S1 = copy.copy(S)
    for j in range(len(br)):
        if (i >> j ) & 1:
            S1[br[j]] = ''
    S2 = ''.join(S1)
    f = True
    for j in range(len(S2)):
        if S2[j] == 'R':
            if j - Kr >= 0:
                if S2[j - Kr] == 'R':
                    f = False
                    break
            if j + Kr < len(S2):
                if S2[j + Kr] == 'R':
                    f = False
                    break
        elif S2[j] == 'B':
            if j - Kb >= 0:
                if S2[j - Kb] == 'B':
                    f = False
                    break
            if j + Kb < len(S2):
                if S2[j + Kb] == 'B':
                    f = False
                    break
    if f:
        ans = max(ans, len(S2))

print(ans)