#include <bits/stdc++.h> using namespace std; int main(){ double sum = 0; double p1 = 1, q1 = 2; sum += q1 / p1; int n; cin >> n; for(int i = 2; i <= n; i++) { double q = p1 + q1; double p = q1; sum += q/ p; p1 = p; q1 = q; } cout << fixed << setprecision(4) << sum; return 0; }