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

		swap(dp, pd);
	}

	printf("%.10f\n", dp[1]);
}