Требуется класс, делегат, перечисление, интерфейс или структура - C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 
namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args);
 
            }
   public int x;
   public int y;
        {
                    double DlinaStoron(Tochka A, Tochka B)
        {
            return Math.Sqrt((B.x - A.x) * (B.x - A.x) + (B.y - A.y) * (B.y - A.y));
        }
 
        double PloshTr(Tochka A, Tochka B, Tochka C)
        {
            double a, b, c, p;
 
            a = DlinaStoron(A, B);
            b = DlinaStoron(B, C);
            c = DlinaStoron(C, A);
 
            p = a + b + c;
 
            return Math.Sqrt(p * (p - a) * (p - b) * (p - c));
        }
       
        double STrap(Tochka A, Tochka B, Tochka C, Tochka D)
        {
            return PloshTr(A, B, C) + PloshTr(A, D, C);
        }
        }
    }