/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.Scanner;
public class Main {
  public static void main (String[] args) 
  {
    Scanner sc = new Scanner(System.in);
    int numOfTestCase = sc.nextInt();
    for (int i = 0; i < numOfTestCase; i++) {
      int n = sc.nextInt();
      long profit = 0;
      int[] stockPrice = new int[n];
      for (int j = 0; j < n; j++) 
        stockPrice[j] = sc.nextInt();
      int currMax = Integer.MIN_VALUE;
      for (int j = n - 1; j >= 0; j--) {
        if (currMax < stockPrice[j]) {
          currMax = stockPrice[j];
        }
        profit += (currMax - stockPrice[j]);
      }
      System.out.println(profit);
 
    }
  }
}
 

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MwozCjUgMyAyCjMKMSAyIDEwMAo0CjEgMyAxIDI=

3
3
5 3 2
3
1 2 100
4
1 3 1 2