public class A1 { public double func1(double i, double j) { return i + j; } } public class A2 extends A1 { public double func1(double i, double j) { return i + j + 10; } } public class A3 extends A2 { public double func1(double i, double j) { return i + j + 20; } } public class B { public static void main(String[] args) { A1 x = new A2(); double res = x.func1(1, 2); System.out.println(res); } } 问以上程序的输出结果是?