def f(A,x):
    c=1
    K=0
    for a in A:
        K+=a*c
        c*=x
    return K

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

s=f(A,0)
t=f(A,1)
u=f(A,-1)

a=(t+u)//2-s
b=(t-u)//2
c=s

if a:
    print(2)
    print(c,b,a)
elif b:
    print(1)
    print(c,b)
else:
    print(0)
    print(c)