'int main()' 之前在这里定义

Question

I did this code and faced an error that I can't understand what it is. I run this program in VS code and compilation was successful but getting an compilation error in GFG portal.

#include <iostream>

using namespace std;
/*
* Create classes Rectangle and RectangleArea
*/
int l,b, result;

class Rectangle
{
   public:
      void display()
      {
        cout<<l <<" "<< b<<endl;
      }
};

class RectangleArea : public Rectangle
{
  public:
    void read_input()
    {
        cin >> l >> b;
    }
    void display()
    {
        result = l* b;
        cout<<result;
    }
};

int main()
{
 /*
 * Declare a RectangleArea object
 */
 RectangleArea r_area;

  /*
  * Read the width and height
  */
  r_area.read_input();

/*
 * Print the width and height
 */
  r_area.Rectangle::display();

  /*
  * Print the area
  */
  r_area.display();

   return 0;
  }

And this is the error I got. Help me.

This is the GFG problem that I'm doing.

Answer 1

不要粘贴主要功能，门户网站将其再次添加到源中，因此它会出现两次。