#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int main() {
	int K;
	cin >> K;
	
	double dp[21];
	dp[0] = 0;
	
	FOR(i, 1, K + 1) {
		double sum = 0;
		FOR(j, 1, 7) if (i - j >= 0) sum += dp[i - j];
		dp[i] = sum / 6 + 1;
	}
	
	printf("%.15f\n", dp[K]);
	return 0;
}