T = int(input())
for _ in range(T):
    N = int(input())
    A = list(map(int, input().split()))
    A.sort()
    ans = 0
    for i in range(N):
        a = A.pop()
        if a<=0:
            break
        if i%2==0:
            ans += a
        else:
            ans -= a
    print(ans)