using default value with same method name

Question

using System;
public class Greet
{
    public void Hello(int a,string j="j")
    {
        Console.WriteLine("1");
    }
    public void Hello(int a)
    {
        Console.WriteLine("2");
    }
}
public class Program
{
    public static void Main()
    {
        Greet obj= new Greet();
        obj.Hello(1);
        Console.WriteLine("Hello World");
    }
}

Which method gets called and why??