k = int(raw_input())
l = [0.0 for _ in range(k+7)]
while k >= 0:
    l[k] = l[k+1]/6 + l[k+2]/6 + l[k+3]/6 + l[k+4]/6 + l[k+5]/6 + l[k+6]/6 + 1
    k -= 1
print l[1]