#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class T, class U> using Pa = pair<T, U>;
template <class T> using vec = vector<T>;
template <class T> using vvec = vector<vec<T>>;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    double P;
    cin >> P;
    if(P==0.0) cout << 0 << "\n";
    else cout << fixed << setprecision(10) << P/(1-P) << "\n";    
}