다음 자바 프로그램의 출력 결과는? class Shape { void draw() { S ystem.out.println("Shape"); } } class Circle extends Shape { void draw() { S ystem.out.println("Circle"); } } class Square extends Shape { void draw() { S ystem.out.println("Square"); } } public class Shapes { public static void main(String[] args) { S hape s1 = new Shape(); C ircle s2 = new Circle(); S quare s3 = new Square(); S hape s; s = s1; s.draw(); s = s2; s.draw(); s = s3; s.draw(); } }