import strutils,sequtils

var
    N = stdin.readline.parseInt
    K = stdin.readline.parseInt
    Pt : array[11,array[70,float64]]
    Pz : array[11,array[70,float64]]
Pt[0][0] = 1
Pz[0][0] = 1
for n in 0..<N:
    for m in n..<60:
        if Pz[n][m] == 0:
            break
        for i in 1..6:
            Pz[n + 1][m + i] += Pz[n][m] / 6
Pt[0..(N - K)] = Pz[0..(N - K)]

for n in (N - K)..<N:
    for m in n..<60:
        for i in 4..6:
            Pt[n + 1][m + i] += Pt[n][m] / 3

var
    ans : float64

for n in N..(6 * N):
    for m in 0..<n:
        ans += Pz[N][m] * Pt[N][n]

echo ans