#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    cout.setf(ios::fixed);
    cout.precision(20);
    double p = 1;
    double x;
    cin >> x;
    for (int i = 1; i < 10000000; i++) {
        p *= exp(1.0 / (x + i) / (x + i));
    }
    cout << log(p) << endl;
}