#include<bits/stdc++.h>
#define rep(i, n) for(ll i = 0; i < (ll)(n); i++)
using namespace std;
typedef long long ll;
typedef double ld;
const ll INF=(1LL<<60);
ld pi=acosl((ld)-1);
const ll mod = 1000000007;
#pragma GCC optimize("Ofast")

template <typename T>ostream &operator<<(ostream &out,const vector<T> &v) {rep(i,(int)v.size()-1)cout<<v[i]<<" ";cout<<v[(int)v.size()-1];return out;}
template <typename T1, typename T2>ostream &operator<<(ostream &out, const map<T1, T2> &p) {out << "(" << p.first << ", " << p.second << ")";return out;}
template <typename T1, typename T2>ostream &operator<<(ostream &out, const pair<T1, T2> &p){out << "(" << p.first << ", " << p.second << ")";return out;}
template<class T>void debag(const T &obj){cout<<obj<<endl;}

using bs=bitset<65>;

bool solve(){
	ld p;cin>>p;
	ld ans=1/(1-p)-1;
	cout<<ans<<endl;
  	return false;
}

signed main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout<<fixed<<setprecision(15);
 solve();
}