#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <iostream>
#include <utility>
#include <set>
#include <cctype>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cmath>

#define INF 1000000000

using namespace std;
typedef long long ll;

double dfs(int k) {
    if (k <= 0) return 0;
    return 1+(1.0/6) * (dfs(k-1)+dfs(k-2)+dfs(k-3)+dfs(k-4)+dfs(k-5)+dfs(k-6));
}

int main(void) {
    int K;
    cin >> K;
    printf("%.10lf\n", dfs(K));
    return 0;
}