#include <iostream>
#include <iomanip>

#define FORR(i,b,e) for(int i=(b);i<(int)(e);++i)
#define FOR(i,e) FORR(i,0,e)
#define dump(var) cerr << #var ": " << var << "\n"
#define dumpc(con) for(auto& e: con) cerr << e << " "; cerr<<"\n"

typedef long long ll;
typedef unsigned long long ull;

using namespace std;

double E[30];

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int K;
    cin >> K;

    E[0] = 0;
    E[1] = 1;

    FORR(k, 2, K+1) {
        double e = 0;
        FORR(i, 1, 7) e += E[max(k-i, 0)];
        E[k] = 1 + e/6;
    }

    cout << fixed << setprecision(5) << E[K] << endl;

    return 0;
}