[BOJ/백준] 11501 주식

T = int(input())
 
for _ in range(T):
    day = int(input())
 
    arr = list(map(int,input().split()))
    answer = 0
    ind = day-1
    max_value = -1
    max_list = []
    while ind >=0:
        if arr[ind] > max_value:
            answer = answer - sum(max_list) + len(max_list)*max_value
            max_list = []
            max_value = arr[ind]
        else:
            max_list.append(arr[ind])
 
        ind -= 1
    if max_list:
        answer = answer - sum(max_list) + len(max_list)*max_value
    print(answer)

 

 

import sys
input = sys.stdin.readline
T = int(input())
 
for _ in range(T):
    N = int(input())
    arr = list(map(int,input().split()))
    max_value = arr[-1]
    answer = 0
    for ind in range(N-2,-1,-1):
        if arr[ind] > max_value:
            max_value = arr[ind]
        else:
            answer = answer + max_value - arr[ind]
    print(answer)