n, s = map(int, input().split())

ANS = []
res = 0
for i in range(1, n + 1):
    res += i
    ANS.append(i)
    if i < s - res <= n:
        ANS.append(s - res)
        break
    elif 0 < s - res <= i:
        j = i - (s - res)
        ANS.pop(j)
        ANS.append(s - res + j + 1)
        break
    elif s - res == 0:
        break

#print(ANS)
if sum(ANS) != s:
    print(-1)
    exit()

print(len(ANS))
print(*ANS)