import sys

sys.setrecursionlimit(10 ** 6)
int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]

def main():
    d=int(input())
    aa=LI()
    if d<3:
        print(d)
        print(*aa)
        exit()
    for i in range(d-2,0,-1):
        aa[i]+=aa[i+2]
    if aa[1:3]==[0,0]:
        print(0)
        print(aa[0])
    elif aa[2]==0:
        print(1)
        print(*aa[:2])
    else:
        print(2)
        print(*aa[:3])

main()