#include <bits/stdc++.h> using namespace std; const int lim = 100; double dp[lim]; int main(){ int k; cin >> k; for(int i=1; i<lim; i++){ for(int j=1; j<=min(6, i-1); j++){ dp[i] += dp[i - j] / 6; } dp[i] += 1; } cout << fixed << setprecision(10) << dp[k] << endl; }