#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <cmath>
#include <numeric>
#include <utility>
#include <iomanip>

using namespace std;
using int64 = long long;

struct aaa{aaa(){cin.tie(nullptr); ios::sync_with_stdio(false); cout<<fixed<<setprecision(20);};}aaa;

int main() {
    double p;
    cin >> p;
    cout << p / (1-p) << endl;
}