N = int(input())
A = list(map(int,input().split()))+[0,0]

for i in range(N, 2, -1):
    A[i-2] += A[i]

if A[2]:
    print(2)
    print(*A[:3])
elif A[1]:
    print(1)
    print(*A[:2])
else:
    print(0)
    print(A[0])