C# method overloading çalışmıyor

int sayi1 = 50;
int sayi2 = 100;

Console.WriteLine(Multiply(sayi1, sayi2));
static int Multiply(int a1 , int a2)
{

 int topla = a1 + a2;
 return topla;
}
static int Multiply(int a1, int a2, int a3)
{

 int topla = a1 + a2 + a3;
 return topla;
}
Console.WriteLine(Multiply(sayi1, sayi2));

public class HelloWorld
{
    int Multiply(int a1 , int a2)
        {

            int topla = a1 + a2;
            return topla;
        }
        int Multiply(int a1, int a2, int a3)
        {

            int topla = a1 + a2 + a3;
            return topla;
         }
       
    public static void Main(string[] args)
    {
        int sayi1 = 50;
        int sayi2 = 100;

        HelloWorld calculater = new HelloWorld();
       
    Console.WriteLine(calculater.Multiply(sayi1, sayi2));
    Console.WriteLine(calculater.Multiply(sayi1, sayi2,sayi1));
   
    }
}

using System;

class mainClass
{
    static int Multiply(int a, int b){ return a + b;}
    static int Multiply(int a, int b, int c){ return a + b + c;}

    public static void Main(string[] args)
    {
        Console.WriteLine(Multiply(1, 2));
        Console.WriteLine(Multiply(1, 2, 3));
        Console.ReadLine();
    }
}