C :

#include <stdio.h>


double fact(int n);

int main(int argc, char const *argv[])
{
	int n ;
	scanf("%d",&n);
	double s = 0;
	for (int i = 1; i <= n; ++i)
	{	
		s += (n-(i-1))/fact(i);
	}
	printf("s=%f\n",s);
	return 0;
}

double fact(int n)
{
	double sum = 1;
	for (int i = 1; i <= n; ++i)
	{
		sum *= i;
	}
	return sum;
}

C++ :

#include<iostream>
using namespace std;

double fact(int);
int main() {
	int n;
	cin >> n;
	double s = 0.0;
	for(int i=1; i<=n; ++i){
		s += (n + 1 - i) / fact(i);
	}
	printf("s=%.6f\n", s);
	return 0;
}

double fact(int x){
	double f = 1.0;
	for(int i=1; i<=x; ++i){
		f *= i;
	}
	return f;
}

C# :

using System;

namespace ACMclubzjicm
{
    class Test_1339
    {
        static void Main()
        {

            int n = GetNum();
            double s = f(n);
            Console.Write("s={0:F6}", s);
            Console.ReadLine();
            return;
        }

        private static int GetNum()
        {
            string stIn = Console.ReadLine().Trim();
            int num = int.Parse(stIn);
            return num;
        }

        private static double f(int n)
        {
            double s = 0;
            for (int i = 1; i <= n; i++)
            {
                s += (double)(n - i + 1) / fat(i);
            }
            return s;
        }

        private static double fat(int n)
        {
            double c = 1;
            for (int i = 1; i <= n; i++)
            {
                c *= i;
            }
            return c;
        }
    }
}