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

lsBR = []
for i in range(len(S)):
    if S[i] == 'B' or S[i] == 'R':
        lsBR.append(i)
ans = 0
for i in range(2**len(lsBR)):
    S1 = copy.copy(S)
    for j in range(len(lsBR)):
        if (i>>j) & 1:
            S1[lsBR[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(len(S2),ans)
print(ans)