Untitled

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int T = sc.nextInt();
        while (T-- > 0) {
            int N = sc.nextInt();
            int[] A = new int[N];
            for (int i = 0; i < N; i++) A[i] = sc.nextInt();
            int l = 0, r = N - 1, leftMax = 0, rightMax = 0;
            long ans = 0;
            while (l < r) {
                if (A[l] < A[r]) {
                    if (A[l] >= leftMax) leftMax = A[l];
                    else ans += leftMax - A[l];
                    l++;
                } else {
                    if (A[r] >= rightMax) rightMax = A[r];
                    else ans += rightMax - A[r];
                    r--;
                }
            }
            System.out.println(ans);
        }
    }
}