from math import gcd
import sys, time, random
from collections import deque, Counter, defaultdict
def debug(*x):print('debug:',*x, file=sys.stderr)
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 61 - 1

def solve():
    n, x = mi()
    c = li()
    maxc = -1
    for i in range(n):
        if not (1 & (x >> c[i])):
            maxc = max(maxc, c[i])
    if maxc == -1:
        print(0)
        return
    else:
        cost = inf
        if x > (1 << (maxc + 1)):
            cost = (x % (1 << (maxc + 1)) + 1)
        cost = min(cost, (x | ((1 << (maxc + 1)) - 1)) - (1 << maxc) + 1 - x)
        print(2 * cost)
            
for _ in range(ii()):
    solve()