#!/usr/bin/env python3

from itertools import product

peter = [0]*(4*9 + 1)
colin = [0]*(6*6 + 1)

for  p in product([1,2,3,4], repeat=9):
    peter[sum(p)] += 1
for p in product([1,2,3,4,5,6], repeat=6):
    colin[sum(p)] += 1

c = 0.0
for i, p in enumerate(peter):
    c += p * sum(colin[:i])

print("{0:.7f}".format(c/(6**6 * 4**9)))