Kr,Kb=map(int,input().split())
S=input()

ans=0
def dfs(idx: int, t: list[str]) -> None:
  if idx==len(S): 
    global ans
    ans=max(ans,len(t))
    return
  
  if S[idx]=='W':
    t+=['W']
    dfs(idx+1,t)
    t.pop()
  
  else:
    dfs(idx+1,t)
    if S[idx]=='R':
      if len(t) < Kr or t[-Kr]!='R':
        t+=['R']
        dfs(idx+1,t)
        t.pop()
    else:
      if len(t) < Kb or t[-Kb]!='B':
        t+=['B']
        dfs(idx+1,t)
        t.pop()

dfs(0,[])
print(ans)