#include <cstdio>
#include <cstring>
#include <cmath>
#include <utility>
#include <iostream>
#include <functional>
#include <bitset>
#include <algorithm>
#include <vector>
#include <forward_list>
#include <set>
#include <map>
#include <queue>
#include <deque>
#include <stack>
#include <numeric>
#include <iomanip>
#define ll long long int
#define pb push_back
#define rep(i,n) for(int i=0;i<(n);i++)
using namespace std;

int mx6[] = {1,0,-1,1,-1,0};
int my6[] = {1,1,1,0,0,-1};

int main(){
    double a; cin >> a;
    cout << fixed << setprecision(10) << a / (1-a) << endl;
}