def main():
    D = int(input())
    a = list(map(int, input().split()))
    a.reverse()


    for idx in range(D-2):
        a[idx], a[idx+2] = 0, a[idx+2] + a[idx]

    if a[-3] != 0:
        print(2)
        print(*reversed(a[-3:]))
        return

    if a[-2] != 0:
        print(1)
        print(*reversed(a[-2:]))
        return

    print(0)
    print(a[-1])


if __name__ == "__main__":
    main()