# 주식

import sys
from collections import deque

input = sys.stdin.readline


def calculate_revenue(n, prices):
    total = 0
    q = deque([prices[0]])
    up = 0
    if prices[0] <= prices[1]:
        up = 1
    else:
        up = 0

    for i in range(1, n):
        if len(q) != 0 and i == n-1 and prices[i] >= q[-1]:
            high = q.pop() if i != n-1 else prices[i]
            while len(q) >= 1 and q[0] > high:
                q.popleft()
            while len(q) >= 1:
                total += (high-q.pop())

        if not up:
            if len(q) != 0 and prices[i] > q[-1]:
                up = 1
            q.append(prices[i])
            continue

        if len(q) != 0 and (prices[i] < q[-1] or i == n-1):
            high = q.pop() if i != n-1 else prices[i]
            while len(q) >= 1 and q[0] > high:
                q.popleft()
            while len(q) >= 1:
                total += (high-q.pop())
            up = 0
        q.append(prices[i])

    return total

def solution():
    t = int(input().rstrip())

    for _ in range(t):
        n = int(input().rstrip())
        prices = list(map(int, input().rstrip().split()))
        print(calculate_revenue(n, prices))

    return


solution()

"""
걸린 시간: 

시간 복잡도: 

해설: 
"""