local mmi, mma = math.min, math.max
local bls, brs = bit.lshift, bit.rshift
local kr, kb = io.read("*n", "*n", "*l")
local s = io.read()
local red, blue = {}, {}
local t = {}
local use = {}
for i = 1, 30 do
  use[i] = true
  t[i] = s:sub(i, i)
  if t[i] == "R" then
    table.insert(red, i)
  elseif t[i] == "B" then
    table.insert(blue, i)
  end
end
local ret = 10
local tot = bls(1, 20)
for i = 0, tot - 1 do
  local ti = i
  for j = 1, 10 do
    local tgt = red[j]
    use[tgt] = ti % 2 == 1
    ti = brs(ti, 1)
  end
  for j = 1, 10 do
    local tgt = blue[j]
    use[tgt] = ti % 2 == 1
    ti = brs(ti, 1)
  end
  local w = {}
  for j = 1, 30 do
    if use[j] then
      table.insert(w, t[j])
    end
  end
  local valid = true
  for j = 1, #w - kr do
    if w[j] == "R" and w[j + kr] == "R" then valid = false break end
  end
  for j = 1, #w - kb do
    if w[j] == "B" and w[j + kb] == "B" then valid = false break end
  end
  if valid then
    ret = mma(ret, #w)
  end
end
print(ret)