#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using P = pair<lint, lint>;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define ALL(a)  (a).begin(),(a).end()
constexpr int MOD = 1000000007;
constexpr int INF = 2147483647;
void yes(bool expr) {
  cout << (expr ? "Yes" : "No") << "\n";
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    double p;
    cin >> p;
    cout << setprecision(10) << (1.0/(1.0-p) - 1) << endl;

}