#include <bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    double answer = 0;
    int K; cin >> K;
    vector<double> dp(K+1); dp.at(K) = 1;
    for(int i=K; i>0; i--){
        answer += dp.at(i);
        for(int k=1; k<=6; k++) if(i-k > 0) dp.at(i-k) += dp.at(i)*0.16666666;
    }

    cout << fixed << setprecision(20) << answer << endl;
}