#include<iostream> #include<iomanip> using namespace std; int main() { int n; cin >> n; float e=0; int k=1; float product=1; for (int i=1; i<=n; i++) { for (int j=1; j<=k; j++) { product*=j; j++; } e+=1.0/product; k++; product=1; } cout << fixed << setprecision(10) << e; }