//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define FIO ios_base::sync_with_stdio(false); cin.tie(0);
#define trav(x,a) for (auto& x: a)
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define mem(a,v) memset((a), (v), sizeof (a))
#define endl "\n"
#define case(t) cout << "Case #" << (t) << ": "
#define reada(a, n) for (int _i = 0; _i < (n); _i++) read(a[_i])
#define pii pair<int, int>
#define pll pair<long long, long long>
#define vii vector<pii>
#define vll vector<pll>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define mp make_pair
#define st first
#define nd second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef cc_hash_table<int,int,hash<int>> ht;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> oset;
const double pi = acos(-1);
const int mod = 1e9 + 7;
const int inf = 1e9 + 7;
const int N = 1e6 + 5;
const double eps = 1e-9;

template<class T> void read(T& x) { cin >> x; }
template<class X, class Y> void read(pair<X,Y>& a) { read(a.first), read(a.second); }
template<class T, size_t U> void read(array<T,U>& x) { for (int i = 0; i < U; i++) read(x[i]); }
template<class T> void read(vector<T>& x) { trav(y, x) read(y); }
template<class T, class... O> void read(T& x, O&... y) { read(x), read(y...); }

string to_string(const char& x) { return string(1,x); }
string to_string(const char*& x) { return (string)x; }
string to_string(const string& x) { return x; }
template<class T, class U> string to_string(const pair<T,U>& x) { return to_string(x.first) + " " + to_string(x.second); }
template<class T, size_t U> string to_string(const array<T,U>& x) { string ret = ""; for (int i = 0; i < U; i++) ret += (!i ? "" : " ") + to_string(x[i]); return ret; }
template<class T> string to_string(const vector<T>& x) { string ret = ""; bool f = 0; trav(y, x) ret += (!f ? "" : " ") + to_string(y), f = 1; return ret; }
template<class T> string to_string(const set<T>& x) { string ret = ""; bool f = 0; trav(y, x) ret += (!f ? "" : " ") + to_string(y), f = 1; return ret; }
void print() { cout << endl; }
template<class T> void pr(const T& x) { cout << to_string(x); }
template<class T, class... O> void print(const T& x, const O&... y) { pr(x); if (sizeof...(y)) pr(" "); print(y...); }

void solve() {
  int n; read(n);
  vector<int> pr, a(n);
  for (int i = 2; i <= 50; i++) {
    int o = 1;
    for (int j = 2; j < i; j++)
      o &= (i % j) != 0;
    if (o)
      pr.push_back(i);
  }
  ll ans = -1;
  read(a);
  for (int i = 0; i < (1 << (sz(pr))); i++) {
    ll v = 1, o = 1;
    for (int j = 0; j < sz(pr); j++)
      if (i >> j & 1)
        v *= (ll)pr[j];
    for (int j = 0; j < n; j++)
      o &= __gcd((ll)a[j], v) > 1;
    if (o) {
      if (ans < 0)
        ans = v;
      else
        ans = min(ans, v);
    }
  }
  print(ans);
}

int main() {
  FIO
  solve();
  // int t; read(t); while (t--) solve();
  return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N = 100;
typedef long long ll;
int a[N], n, isnot[N];
vector<int>G[N];
int vis[N];
int b[] = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29,  31, 37, 41, 43, 47 };
ll ans = LLONG_MAX;
void dfs(int p, ll sum) {
    if (p >= 15) {
        for (int i = 1; i <= n; i++) {
            if (__gcd(sum, 1ll*a[i]) == 1) {
                return;
            }
        } 
        ans = min(ans, sum);
        return;  
        
    }
    dfs(p + 1, sum * b[p]);
    dfs(p + 1, sum);
}



int main() {
    
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        //a[i] = i + 1;
       // sort(G[a[i]].begin(), G[a[i]].end());
    }
    dfs(0, 1);
   
    cout << ans << endl;
    return 0;
}

//2 3 5 7 11 13 17 19 23 29  31 37 41 43 47 