#include <bits/stdc++.h>
using namespace std;
using ll = long long;

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


int main(){
    int n;  cin >> n;
    vector<ll> a(n);
    for(auto& x : a){
        cin >> x;
    }
    sort(a.begin(), a.end());

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

    ll ans = 1ll << 62;
    do{
        ll t = (n == 2) ? f(a[0], a[1]) : f(f(a[0], a[1]), a[2]);
        if(ans <= t){
            continue;
        }
        ans = t;
    }while(next_permutation(a.begin(), a.end()));

    cout << ans << endl;
    return 0;
}