11078 Open Credit System

import java.util.Scanner;

class Another {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int testCases = scanner.nextInt();
        while (testCases-- > 0) {
            int studentNumber = scanner.nextInt();
            int numbers[] = new int[studentNumber];
            for (int i=0;i<studentNumber;i++) {
                numbers[i] = scanner.nextInt();
            }
            
            int max = -1000000;
            int highest = -1000000;

            for (int i=0;i<numbers.length;i++) {
                int num = highest-numbers[i];
                if (num > max) max = num;
                if (numbers[i] > highest) highest = numbers[i];
            }
            System.out.println(max);
        }

    }

}