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<>();
        Pair<String> p1 = new Pair<>("hello", "cheers");
        Pair<Boolean> p2 = new Pair<>(true, false);
        Pair<Integer> p3 = new Pair<>(123, 456);
        Pair<Number> p4 = new Pair<>(123, 456); 
        Pair<Object> p5 = new Pair<>(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);

    }
}