import sys
input=lambda:sys.stdin.readline().rstrip()
K=list(map(int,input().split()))
S=[['R','B','W'].index(i) for i in input()]
ans=0
for i in range(2**20):
	temp=i
	cur=[]
	for j in S:
		if j==2 or temp%2:
			cur.append(j)
		if j<2:
			temp//=2
	flg=1
	for j in range(2):
		for k in range(len(cur)-K[j]):
			if cur[k]==cur[k+K[j]]==j:
				flg=0
	ans=max(ans,len(cur)*flg)
print(ans)