// Write a program that inputs positive integer n and prints real number equals to

//    1/0! + 1/1! + 1/2! + … + 1/n!

using System;

using System.Diagnostics;

public class Program

{

    public static int InputInt(string prompt)

    {

        Console.Write("Enter " + prompt + ":");

        return Convert.ToInt32(Console.ReadLine());

    }

    public static void Main(string[] args)

    {

        int n = InputInt("n");

        Trace.Assert(n >= 0);

        int r = 1;

        int i = 0;

        double q = 1.0;

        // invariant: r = i! and q = 1/0! +...+ 1/i! and 1<=i<=n

        while (i != n)

        {

            // r = i! and i<n

            i = i + 1;

            // r = (i - 1)! and q = 1/0! +...+ 1/(i-1)! and i<=n

            r = r * i;

            // r = (i - 1) * i = i! and q = 1/0! +...+ 1/(i-1)! and i<=n

            q = q + 1.0/r;

            // r = i! and q = 1/0! +...+ 1/i! and i<=n

        }

        // r = n! and q = 1/0! +...+ 1/n!

        Console.Write("Sum = " + q);

    }

}