def judge(S):
    global Kr
    global Kb
    for i in range(len(S)):
        if S[i]=='R' and i+Kr < len(S) and S[i+Kr] == 'R':
            return False
        if S[i]=='B' and i+Kb < len(S) and S[i+Kb] =='B':
            return False
    return True

def rec(S):
    global ans
    if S in used or len(S) < ans:
        return
    used.add(S)
    if judge(S):
        ans= max(ans,len(S))
        return
    for i in range(len(S)):
        if S[i]!='W':
             rec(S[:i]+S[i+1:])

Kr,Kb=map(int,raw_input().split())
S=raw_input()
ans =0
used = set([])
rec(S)
print ans