r,b=map(int,input().split())
S=input()

def cond(A):
    for i in range(len(A)):
        if i+r<len(A) and A[i]==A[i+r]=="R":
            return False
        if i+b<len(A) and A[i]==A[i+b]=="B":
            return False
    return True

ANS=0
for i in range(1<<20):
    A=[]
    count=0
    for j in range(len(S)):
        if S[j]=="W":
            A.append("W")
        else:
            if (1<<count) & i != 0 :
                A.append(S[j])
            count+=1

    if cond(A)==True:
        ANS=max(ANS,len(A))

print(ANS)