17 class A {}  class
18 class B1 extends A {}
19 class B2 extends A {}
36     A a = new A();  in main()
37     A b1 = new B1();  in main()
38     A b2 = new B2();  in main()
39     A c1 = new C1();  in main()
40     A c2 = new C2();  in main()
41     A f1 = new F1();  in main()
42     A f2 = new F2();  in main()
43     A g1 = new G1();  in main()
44     A g2 = new G2();  in main()