#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    double p;
    cin >> p;
    cout << fixed << setprecision(6) << 1. / (1. - p) - 1. << endl;

    return 0;
}