27.3

pr = 1000001
d = 6
n = int(input())
k = 0
b = [1000001] * 6
c = [1000001] * 6
b[0] = int(input())
if b[0]%2 == 0:
    c[0] = b[0]
    k = 1
else:
    c[0] = 1001
for i in range(1, d):
    x = int(input())
    b[i] = min(min(b), x)
    if x%2 == 0:
        c[i] = min(min(c), x)
        k = 1
    else:
        if k == 1:
            c[i] = min(c)
        else:
            c[i] = 1001
for i in range(d, n):
    x = int(input())
    if x%2 == 0:
        if x*b[0] < pr:
            pr = x * b[0]
    else:
        if c[0] != 1001:
            if x*c[0] < pr:
                pr = x*c[0]
    for j in range(d-1):
        b[j] = b[j+1]
        c[j] = c[j+1]
    b[d-1] = min(min(b), x)
    if x%2 == 0:
        c[d-1] = min(min(c), x)
    else:
        min(c)
if pr == 1000001:
    print(-1)
else:
    print(pr)