import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;
public class Solution {
// Complete the stockmax function below.
static long stockmax(long[] prices) {
long max = 0;
long profit = 0;
for(int i = prices.length - 1; i >= 0; i--) {
if(prices[i] > max) {
max = prices[i];
}
profit += (max - prices[i]);
}
return profit;
}
private static final Scanner scanner = new Scanner(System.in);
public static void main(String[] args) throws IOException {
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));
int t = scanner.nextInt();
scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
for (int tItr = 0; tItr < t; tItr++) {
int n = scanner.nextInt();
scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
String[] pricesItems = scanner.nextLine().split(" ");
n = pricesItems.length;
long[] prices = new long[n];
scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
for (int i = 0; i < n; i++) {
long pricesItem = Long.parseLong(pricesItems[i]);
prices[i] = pricesItem;
}
long result = stockmax(prices);
System.out.println(result);
bufferedWriter.write(String.valueOf(result));
bufferedWriter.newLine();
}
bufferedWriter.close();
scanner.close();
}
}
