n = int(input())
a = [0] * n
for i in range(n):
    a[i] = int(input())
Max = a[0]
P = -1
for i in range(8, n):
    if a[i - 8] > Max:
        Max = a[i - 8]
    if Max * a[i] > P:
        P = Max * a[i]
print(P)