D = int(input())
A = list(map(int, input().split()))
fn1, f0, f1 = 0, A[0], 0
sign = 1
for i in range(D+1):
    f1 += A[i]
    fn1 += sign * A[i]
    sign *= -1
a, b, c = (f1 + fn1 - 2 * f0) // 2, (f1 - fn1) // 2, f0
if a != 0:
    print(2)
    print(c, b, a)
else:
    if b != 0:
        print(1)
        print(c, b)
    else:
        print(0)
        print(c)