import sys
from math import gcd
from itertools import permutations
from functools import reduce
input = sys.stdin.readline

n = int(input())
a = list(map(int, input().split()))

if(n >= 4):
    exit(print(0))

def f(x, y):
    if(gcd(x, y) == 1):
        return (x - 1) * (y - 1)
    return 0

ans = 10 ** 18
for p in permutations(a):
    ans = min(ans, reduce(f, p))
print(ans)