Greatest in list

package com.company;


import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        ArrayList<Integer> numbers = new ArrayList<>();

        while (true) {
            int input = Integer.valueOf(scanner.nextLine());

            if (input == -1) {
                break;
            }
            numbers.add(input);
        }

        int greatest = numbers.get(0);

        for (int i = 0; i < numbers.size(); i++) {
            int number = numbers.get(i);
            if (greatest < number) {
                greatest = number;
            }
        }

        System.out.println("The greatest number is " + greatest);

    }
}