#include <stdio.h> #include <iostream> #include <string.h> #include <string> #include <algorithm> #include <iomanip> #include<vector> #include<math.h> //#include<bits/stdc++.h> using namespace std; int main() { double a = 2, b = 1; int n; cin >> n; double sum=0; double t; while (n--) { sum += a / b; t = a; a = a + b; b = t; } cout << fixed << setprecision(6) << sum; } |
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