def solve():
    n, x = map(int, input().split())
    C = list(map(int, input().split()))
    while C and (x >> C[-1]) & 1:
        C.pop()

    if not C:
        print(0)
        return

    c = C[-1]
    if x < (1 << c):
        ans = (1 << c) - x
        print(2 * ans)
        return

    t = x & ((1 << c) - 1)
    ans = min(t + 1, (1 << c) - t)
    print(2 * ans)


for _ in range(int(input())):
    solve()