import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter x: ");
        int x = in.nextInt();
        double sum = 0;
        
        for (int i = 2; i <= 20; i++) {
            double f = 1;
            for (int j = 1; j <= i; j++) {
                f *= j;
            }
            sum += x / f;
        }
        System.out.println("Sum = " + sum);
        
    }
}