D = int(input())
l = list(map(int, input().split()))

while len(l) > 3:
    l[-3] += l[-1]
    l.pop()

if len(l) < 3:
    print(l[0])
else:
    if l[2] != 0:
        print(2)
        print(l[0],l[1],l[2])
    else:
        if l[1] != 0:
            print(1)
            print(l[0],l[1])
        else:
            print(0)
            print(l[0])