Kr,Kb = map(int,input().split())
S = input()
ans = 0
for i in range(1<<20):
    lis = []
    R,B = divmod(i,1<<10)
    r = 0
    b = 0
    for s in S:
        if s == "W":
            lis.append(s)

        if s == "R":
            if R >> r & 1:
                lis.append(s)
            r += 1

        if s == "B":
            if B >> b & 1:
                lis.append(s)
            b += 1

    ok = 1
    for i,s in enumerate(lis):
        
        if s == "B" and i >= Kb and lis[i-Kb] == "B":
            ok = 0

        if s == "R" and i >= Kr and lis[i-Kr] == "R":
            ok = 0
        
    if ok:
        ans = max(ans,len(lis))
print(ans)