#include "bits/stdc++.h"
using namespace std;
#define ll long long int
#define rep(i,n) for( int i = 0; i < n; i++ )
#define rrep(i,n) for( int i = n; i >= 0; i-- )
#define REP(i,s,t) for( int i = s; i <= t; i++ )
#define RREP(i,s,t) for( int i = s; i >= t; i-- )
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define INF 2000000000
#define mod 1000000007
#define INF2 1000000000000000000

unsigned int randInt() {
	static unsigned int tx = 123456789, ty = 362436069, tz = 521288629, tw = 88675123;
	unsigned int tt = (tx ^ (tx << 11));
	tx = ty; ty = tz; tz = tw;
	return (tw = (tw ^ (tw >> 19)) ^ (tt ^ (tt >> 8)));
}
int main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
	int K; cin >> K;
	int sum = 0;
	rep(i, 10000000) {
		int tmp = 0;
		while (tmp < K) {
			tmp += randInt() % 6 + 1;
			sum++;
		}
	}
	cout << sum / 10000000.0 << endl;

    return 0;
}