C++ หาค่าประมาณค่า e

double d(int m)
{
double x = 1;
for (int i = 1; i <= m; i++)
{
x = x*i;
}
return x;
}
int main()
{
        int n;
double ex=0;

cout << "Enter Input : ";
cin >> n;

for (int i = 0; i <=n; i++)
{
ex = ex + (1.0 / d(i));
cout << setprecision(50);
cout <<"e = "<< ex << endl;
}
        return 0;
}