What will be the output of the following C++ code?

#include <iostream>
using namespace std;
long factorial (long a)
{
    if (a > 1)
        return (a * factorial (a + 1));
    else
        return (1);
}
int main ()
{
    long num = 3;
    cout << num << "! = " << factorial ( num );
    return 0;
}