#include <bits/stdc++.h>
#define all(x) x.begin(), x.end()
using namespace std;
using ll = long long;

ll gcd(ll a, ll b) {
	while (b != 0) {
		ll r = a % b;
		a = b;
		b = r;
	}
	return a;
}

ll f(ll x, ll y) {
	return (gcd(x, y) == 1) ? (x - 1) * (y - 1) : 0;
}


int main(void) {
	int n;	cin >> n;

	if (n >= 4) {
		cout << 0 << endl;
		return 0;
	}

	vector<ll> a(n);
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	sort(all(a));

	ll ans = 1000000000000000001ll;
	do {
		ll t = f(a[0], a[1]);
		if (n == 3) {
			t = f(t, a[2]);
		}
		if (ans <= t) {
			continue;
		}
		ans = t;
	} while (next_permutation(all(a)));

	cout << ans << endl;

    return 0;
}