import sys, time, random
from collections import deque, Counter, defaultdict
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353
import itertools
from math import gcd

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

a = li()

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


ans = inf
if n == 3:
    for v in itertools.permutations(a):
        ans = min(ans, f(f(v[0], v[1]), v[2]))
else:
    ans = f(a[0], a[1])

print(ans)