local n, k = io.read("*n", "*n")
local div1 = 6^n
local div2 = 3^k * 6^(n-k)
local t1, t2 = {}, {}
for i = 1, 6 * n do t1[i], t2[i] = 0, 0 end
local curmin, curmax = 0, 0
local fst = true
for i = 1, k do
  if(fst) then
    fst = false
    for j = 4, 6 do t1[j] = 1 end
    curmin, curmax = 4, 6
  else
    for s = curmax, curmin, -1 do
      for j = 6, 4, -1 do
        t1[s + j] = t1[s + j] + t1[s]
      end
      t1[s] = 0
    end
    curmin, curmax = curmin + 4, curmax + 6
  end
end
for i = k + 1, n do
  if(fst) then
    fst = false
    for j = 1, 6 do t1[j] = 1 end
    curmin, curmax = 1, 6
  else
    for s = curmax, curmin, -1 do
      for j = 6, 1, -1 do
        t1[s + j] = t1[s + j] + t1[s]
      end
      t1[s] = 0
    end
    curmin, curmax = curmin + 1, curmax + 6
  end
end
curmin, curmax, fst = 0, 0, true
for i = 1, n do
  if(fst) then
    fst = false
    for j = 1, 6 do t2[j] = 1 end
    curmin, curmax = 1, 6
  else
    for s = curmax, curmin, -1 do
      for j = 6, 1, -1 do
        t2[s + j] = t2[s + j] + t2[s]
      end
      t2[s] = 0
    end
    curmin, curmax = curmin + 1, curmax + 6
  end
end
for i = 2, 6 * n do
  t2[i] = t2[i] + t2[i - 1]
end
local p = 0
for i = 2, 6 * n do
  p = p + t1[i] / div1 * t2[i - 1] / div2
end
print(string.format("%.8f", p))