#include <iostream> #include <iomanip> using namespace std; int main() { int n; cin >> n; double sum = 0.0; double a = 1, b = 2; for (int i = 1; i <= n; i++) { sum += b / a; double t = a + b; a = b; b = t; } cout << fixed << setprecision(4) << sum << endl; return 0; }