using System;

class D : IDisposable{
  IDisposable a = null;
  IDisposable b = null;
  public void Dispose(){
    using(a)
    using(b)
    {}
  }
}

public class Test{
  public static void Main(){
    try{
      using(D d = new D()){
        Console.WriteLine("using D");
      }
    }
    catch(Exception e){Console.WriteLine("catch");}
  }
}