import java.util.Scanner;

public class Solution 
{
    private Scanner in;
    
    
    public Solution()
    {
        in = new Scanner(System.in);
        
    }
    
    public void run()
    {
        int testCases = in.nextInt();
        for(int test=0; test<testCases; test++)
        {
            int n = in.nextInt();
            int[] arr = new int[n];
            int[] dp = new int[n];
            for(int i=0; i<n; i++)
                arr[i] = in.nextInt();
            int max = arr[n-1];
            for(int i=n-1; i>=0; i--)
            {
                max = (arr[i]>max)?arr[i]:max;
                dp[i] = max;
            }
            long sum = 0;
            for(int i=0; i<n; i++)
            {
                sum += (dp[i] - arr[i]);
            }
            System.out.println(sum);
        }
    }
    
    public static void main(String[] args)
    {
        Solution solution = new Solution();
        solution.run();
    }
}

long stockmax(vector<int> p) {
    long ans = 0; int max_num = 0;
    for(int i = p.size() - 1; i >= 0; i--) 
    {
        max_num = max(max_num, p[i]);
        ans += max(0, max_num - p[i]);
    }
    return ans;
}

def stockmax(prices):
    profit = 0
    maxPrice = 0
    for price in prices[::-1]:
        if price > maxPrice:
            maxPrice = price
        else:
            profit += maxPrice - price
    return profit