import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################


# 2 ** (c[i] + 1) * k + 2 ** c[i] >= x
def f(c, x):
    return ((x - 2 ** c- 1) // (2 ** (c + 1)) + 1) * (2 ** (c + 1)) + 2 ** c

# 2 ** (c[i] + 1) * k - 1 <= x

def g(c, x):
    if x < 2 ** c:
        return -10 ** 18
    return ((x + 1) // (2 ** (c + 1))) * (2 ** (c + 1)) - 1
# 1, 3, 
# 2, 3, 6, 7
for _ in range(ni()):
    n, x = na()
    c = na()
    
    for i in range(n-1,-1,-1):
        if x >> c[i] & 1:
            continue
        else:
            #print(c[i])
            print(2 * min(f(c[i], x) - x, x - g(c[i], x)))
            break
    else:
        print(0)