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)