#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <iomanip>
#include <assert.h>
#include <array>
#include <cstdio>
#include <cstring>
#include <random>
#include <functional>
#include <numeric>
#include <bitset>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
template<class T1, class T2> inline bool minimize(T1 &a, T2 b) { return b < a && (a = b, 1); }
template<class T1, class T2> inline bool maximize(T1 &a, T2 b) { return a < b && (a = b, 1); }

typedef long long ll;
int const inf = 1<<29;

double E[100];

int main() {

  int K; cin >> K; K+=50;
  rep(i, 6) E[K+i] = 0;
  for(int x=K-1; x>=0; x--) {
    E[x]=E[x+1]*1/6+E[x+2]*1/6+E[x+3]*1/6+E[x+4]*1/6+E[x+5]*1/6+E[x+6]*1/6+1;
  }

  printf("%.9f\n", E[50]);

  return 0;
}