import sequtils, strutils

let
  k = parseInt stdin.readLine

var
  dp = (-1.0).repeat k+6

for i in k ..< k+6:
  dp[i] = 0.0

for i in countdown(k-1, 0):
  var tmp = 1.0
  for j in 1 .. 6:
    tmp += dp[i+j] / 6
  dp[i] = tmp

echo dp[0]