N, S = map(int, input().split())
SS = (1 + N) * N // 2
SS -= S
A = [i + 1 for i in range(N)]
ans = []
for i in range(N - 1, -1, -1):
    if SS >= A[i]:
        SS -= A[i]
    else:
        ans.append(A[i])
ans.sort()
print(len(ans))
print(*ans)