#include <iostream> #include <cstdio> #include <cmath> #include <ctime> #include <cstdlib> #include <cassert> #include <vector> #include <list> #include <stack> #include <queue> #include <deque> #include <map> #include <set> #include <bitset> #include <string> #include <algorithm> #include <utility> #define llint long long #define inf 1e18 #define rep(x, s, t) for(llint (x) = (s); (x) < (t); (x)++) #define Rep(x, s, t) for(llint (x) = (s); (x) <= (t); (x)++) #define chmin(x, y) (x) = min((x), (y)) #define chmax(x, y) (x) = max((x), (y)) using namespace std; typedef pair<llint, llint> P; double p; int main(void) { ios::sync_with_stdio(0); cin.tie(0); cin >> p; printf("%.11f\n", 1/(1-p)-1); return 0; }