#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)



int K;
//-----------------------------------------------------------------
int main() {
	cin >> K;

	vector<double> dp(201, 0);
	rep(t, 0, 10000) {
		vector<double> pd(201, 0);

		rep(i, 1, K + 1) {
			double tmp = 0;
			rep(j, 1, 7) {
				if (i - j < 0) tmp += dp[K];
				else tmp += dp[i - j];
			}
			pd[i] = tmp / 6 + 1;
		}

		swap(dp, pd);
	}

	printf("%.10f\n", dp[K]);
}