static field initialization how takes place

Please go through below example:
 
Here there are three classes Test, First, second. 
In Test class it displays output which depends on First and Second.
First class declares a static variable called X which calls static function of class Test .
In same way class Second declares a static variable called Y which calls static function of class Test 
 
 
using System;
class Test
{
   static void Main() {
      Console.WriteLine("{0} {1}", Second.Y, First.X);
   }
   public static int F(string s) {
      Console.WriteLine(s);
      return 1;
   }
}

class First
{
   public static int X = Test.F("First A");
}

class Second
{
   public static int Y = Test.F("Second A");
}
 
Output: 
First A 
Second A
1 1
Because the execution of X's initializer and Y's initializer could occur in either 
order; they are only constrained to occur before the references to those fields.