Write a C++ program to find the factorial of a number

#include < iostream >
using namespace std;
int main()
{
int n;
long factorial = 1.0;
cout << "Enter a positive integer: ";
cin >> n;
if (n < 0)
cout << "Error! Factorial of a negative number doesn't exist.";
else
{
for(int i = 1; i <= n; ++i)
{
factorial *= i;
}
cout << "Factorial of " << n << " = " << factorial;
return 0;
}