C# two classes with static members referring to each other

I wonder why this code doesn't end up in endless recursion. I guess it's connected to the automatic initialization of static members to default values, but can someone tell me "step by step" how does 'a' get the value of 2 and 'b' of 1?

public class A
{
    public static int a = B.b + 1;
}
public class B
{
    public static int b = A.a + 1;
}

static void Main(string[] args)
{
    Console.WriteLine("A.a={0}, B.b={1}", A.a, B.b); //A.a=2, B.b=1
    Console.Read();
}