Professor put another main() inside of main() [closed]

For a lab my professor for C++ gave us an application file to test our Array class but it has another main inside of main and I've never seen that before. I was wondering if that is legal since it is giving me an error that it expected a ; after the braces under the 2nd main(). so here's the code.

    int main()
{
     int main()
{

      // Creation of an array
      Array array1(10);
      array1.insert(5);
      array1.insert(3);
      array1.insert(2);
      cout << "Array 1: " << endl;
      array1.print();
      cout << endl;
      // Creation of another array    
      Array array2(20);
      for (int i = 0; i < 20; i++)
      {
           array2.insert(i  10);
      }
      cout << "Array 2: " << endl;
      array2.print();
      cout << endl;
      return 0;
 }

}

This is a picture of the code as well that was given