// This program repeatedly reads integers from the user
// until a non-negative number is entered, then squares the number.

import java.util.*;

public class NonNegativeInput {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        System.out.print("Type a non-negative integer: ");
        int number = console.nextInt();
        
        // check for negative numbers
        while (number < 0) {
            System.out.print("Invalid number, try again: ");
            number = console.nextInt();
        }
        
        System.out.println(number + " squared is " + (number * number));
    }
}