#include <cstdio>
#include <vector>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
#define repeat_reverse(i,n) for (int i = (n)-1; (i) >= 0; --(i))
using namespace std;
int main() {
    int k; scanf("%d", &k);
    vector<double> e(k+6);
    vector<double> p(k+6);
    e[k  ] = 0; p[k  ] = 1;
    e[k+1] = 0; p[k+1] = 0;
    e[k+2] = 0; p[k+2] = 0;
    e[k+3] = 0; p[k+3] = 0;
    e[k+4] = 0; p[k+4] = 0;
    e[k+5] = 0; p[k+5] = 0;
    repeat_reverse (i,k) {
        e[i] = 1;
        p[i] = 0;
        repeat (j,6) {
            e[i] += e[i+1+j] / 6;
            p[i] += p[i+1+j] / 6;
        }
    }
    double ans = e[0] / p[0];
    printf("%.12lf\n", ans);
    return 0;
}