#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1e9;
int MOD = 1e9+7;
main(){
    int K;
    ll sum = 0,cnt = 0;
    cin >> K;
    while(sum < 5000000){
        int num = 0;
        while(num != K){
            num += rand() % 6 + 1;
            if(num > K)num = 0;
            sum++;
        }
        cnt++;
    }
    cout << 1.* sum / cnt << endl;
}