#include <iostream> #include <iomanip> // Needed for setprecision using namespace std; int main() { int n; // 1. Read the input number n cin >> n; // 2. Define variables and initialize double sum = 0.0; // Total sum starts at 0 double numerator = 2.0; // First term's numerator double denominator = 1.0; // First term's denominator double current_term; // Current term's value double old_numerator; // To store old numerator when updating // 3. Loop n times to calculate each term and sum for (int i = 1; i <= n; i++) { // Calculate current term current_term = numerator / denominator; // Add current term to sum sum = sum + current_term; // Update numerator and denominator for next term old_numerator = numerator; // Save old numerator numerator = old_numerator + denominator; // New numerator denominator = old_numerator; // New denominator } // 4. Output sum with 4 decimal places cout << fixed << setprecision(4) << sum << endl; return 0; }