#include <iostream>
#include <vector>
#include <string>
#include <utility>
#include <algorithm>
#include <climits>

using namespace std;

int main() {
    double p;
    cin >> p;
    cout << p / (1-p) << endl;
}
/*
e = p + pe
e - pe = p
e(1-p) = p
e = p / (1-p)
*/