#include <cmath>
#include <cstdio>
#include <iostream>
using namespace std;

int main() {
    double N;
    cin >> N;
    double ans = 0;
    for (double i = 1.0; i <= 6.0; i++) {
        ans += 1.0 / pow(i, N);
    }
    printf("%.7f", ans);
}