#include <iostream>
#include <iomanip>
#include <cmath>

using ldouble = long double;

void solve() {
    ldouble p;
    std::cin >> p;

    std::cout << std::fixed << std::setprecision(10)
              << p / (1 - p) << "\n";
}

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

    solve();

    return 0;
}