#include <bits/stdc++.h>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

int main() {
	double x; cin >> x;
	cout << (1. / (1. - x) - 1.) << endl;
	return 0;
}