#include <bits/stdc++.h>

using namespace std;

using ll = long long;

constexpr char newl = '\n';

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    long double p;
    cin >> p;
    p = 1 - p;
    cout << fixed << setprecision(15) << 1 / p - 1 << newl;

    return 0;
}