minEven = 1002**2
minFact = 1001**2
minOdd = 1003**2
fact1 = 0
fact2 = 0
queue = [0]*6

def push(element, queue,size):
     a = queue[1]
     for i in range(1,size-1):
         queue[i] = queue[i+1]
     queue[size-1] = queue[0]
     queue[0] = element
     return a

n = int(input())
for i in range(1,7):
    a  =int(input())
    queue[i%6] = a

for i in range(7,n+1):
    b = int(input())
    a = push(b,queue,len(queue))
    if a %2 == 0 and a <minEven:
        minEven = a
    if a%2!=0 and a < minOdd:
        minOdd=a
    fact1 = b*minEven
    fact2 = b*minOdd
    k = min(fact1,fact2)
    if k%2==0:
        minFact = min(minFact,k)
    else:
        minFact = min(minFact,fact1)


if(minFact !=1001**2):
    print(minFact)
else:
    print(str(-1))