class Pair<T> {
	private T first;
	private T second;

	public Pair() {
	} // first and second automatically initialized as null

	public Pair(T x1, T x2) {
		first = x1;
		second = x2;
	}

	@Override
	public String toString() {
		return "(1)" + first + " (2)" + second;
	}
}

public class Main {
	public static void main(String[] args) {
		Pair<String> p0 = new Pair<String>();
		Pair<String> p1 = new Pair<String>("hello", "cheers");
		Pair<Boolean> p2 = new Pair<Boolean>(true, false);
		Pair<Integer> p3 = new Pair<Integer>(123, 456);
		Pair<Number> p4 = new Pair<Number>(123, 456);
		Pair<Object> p5 = new Pair<Object>(123, "cheers");
		
        //Error: The constructor Pair<Integer>(int, String) is undefined
        // Pair<Integer> p6 = new Pair<Integer>(123,"cheers"); 
        
		System.out.println(p0);
		System.out.println(p1);
		System.out.println(p2);
		System.out.println(p3);
		System.out.println(p4);
		System.out.println(p5);

	}
}

// (1)null (2)null
// (1)hello (2)cheers
// (1)true (2)false
// (1)123 (2)456
// (1)123 (2)456
// (1)123 (2)cheers