文件目录

#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
    int n;
    cin >> n;
    int p = 1, q = 2, t;
    double s = 0;
    for (int i = 1; i <= n; i++)
    {
        s += 1.0 * q / p;
        t = p + q;
        p = q;
        q = t;
    }
    cout << fixed << setprecision(4) << s;
    return 0;
}