Hier der code:

#include <iostream>
#include <conio.h>
using namespace std;

double fak(int);

int main(){
	double n;
	long double e = 1;
	long double temp;
	cout<<"Wie gross soll \"n\" sein, je groesser es ist um so genauer wird e:";
	cin>>n;
	for(int i = 1; i <= n; i++){
		temp = 1/fak(i)	;
		e = e + temp;
	}
	cout<<"e="<<e;
	getch();
	return 0;
}
double fak(int i){
	double x = i-1;
	double res = i;
	while (x > 1){
		res *= x;
		x--;
		}  
	return res;
}