n, m = map(int, input().split())
A = sorted([int(a) for a in input().split()])
B = [not i for i in range(n)]
C = []
for i in range(1, n):
    if A[i] * (n-1) < m:
        print(-1)
        exit(0)
    if not B[i]:
        k = A[i] * 2
        for j in range(i+1, n):
            if A[j] > k:
                print(-1)
                exit(0)
            if A[j] == k:
                B[j] = True
                k += A[i]
        C.append(A[i])
print(len(C))
print(*C)