import sys
#sys.setrecursionlimit(n)
import heapq
import re
import bisect
import random
import math
import itertools
from collections import defaultdict, deque
from copy import deepcopy
from decimal import *

mx = 0
kr, kb = (int(i) for i in input().split())
s = list(input())
k = deque()
def solve(i):
    global mx
    if i == len(s):
        mx = max(mx, len(k))
        return 0
    if s[i] != 'W':
        solve(i + 1)
    size = len(k)
    flag = False
    if (s[i] == 'R' and (size - kr < 0 or k[size - kr] != 'R')):
        k.append(s[i])
        flag = True
    if (s[i] == 'B' and (size - kb < 0 or k[size - kb] != 'B')):
        k.append(s[i])
        flag = True
    if s[i] == 'W':
        k.append(s[i])
        flag = True

    if flag:
        solve(i + 1)
        k.pop()
solve(0)
print(mx)