T=int(input())
for _ in range(T):
  n,x=map(int,input().split())
  c=list(map(int,input().split()))
  for i in reversed(range(n)):
    if (x>>c[i])&1==0:
      r=((x>>c[i])+1)<<c[i]
      if x<(1<<c[i]):
        print((r-x)*2)
      else:
        print(min(r-x,x-(r-(1<<c[i])-1))*2)
      break
  else:
    print(0)