def Dequeqe():
    a = queue[0]
    del queue[0]
    return a

n = int(input())
queue = []
for i in range (0, 7):
    queue.append(int(input()))
minc = 1001**2
minn = 1001**2
minp = 1001**2
for i in range (7, n):
    x = int(input())
    b = Dequeue()
    if b % 2 == 0:
        if b < minc: minc = b
    elif b < minn: minn = b
    if x % 2 == 0:
    k = min(minc, minn)
        if minp < x * k: minp = x*k
    elif minp < x * minc: minp = x * minc

if minp == 1001**2:
    print('-1')
else
    print(minp)