#include using namespace std; typedef long long ll; template bool chmin(T1 &a,T2 b){if(a<=b)return 0; a=b; return 1;} template bool chmax(T1 &a,T2 b){if(a>=b)return 0; a=b; return 1;} int dx[4]={0,1,0,-1}; int dy[4]={1,0,-1,0}; long double eps = 1e-9; long double pi = acos(-1); signed main(){ ios::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(20); double p; cin>>p; p = 1.0-p; cout << 1.0/p - 1.0 << endl; }