interface Calc {
	int add(int op1, int op2);
	int multiply(int op1, int op2);
	// ....
}

class CalcImpl implements Calc {
	public int add(int op1, int op2) {
		return op1+op2;
	}
	public int multiply(int op1, int op2) {
		return op1*op2;
	}
}

public class CalcTest {
	public static void main(String[] args) {
		Calc c = new CalcImpl();
		Out.println("3+2=" + c.add(3, 2));
		Out.println("4*4=" + c.multiply(4,4));
	}
}