    /**   Created by: Humberto Yusta
          Codeforces User: humbertoyusta
          Country: Cuba                    */
#include<bits/stdc++.h>
using namespace std;
/// Pragmas
#pragma GCC optimize("Ofast","unroll-loops","omit-frame-pointer","inline","03") // Optimization flags
//#pragma GCC option("arch=native","tune=native","no-zero=upper") // Enable AVX
//#pragma GCC target("avx2") // Enable AVX
//#pragma comment(linker, "/STACK:1024000000,1024000000") // Increase stack limit
//#pragma GCC target("sse,sse2,sse,ssse3,sse4,popcnt,abm,mmx,avx,tune=native") // I don't know what it is
/// Macros:
#define int long long
#define f first
#define s second
#define db(x) cerr << #x << ": " << (x) << '\n';
#define pb push_back
#define lb lower_bound
#define up upper_bound
#define all(x) x.begin() , x.end()
#define rall(x) x.rbegin() , x.rend()
#define enl '\n'
typedef pair<int,int> ii;
typedef long double ld;
typedef unsigned long long ull;
/// Constraints:
const int maxn = 1000010;
const int mod = 1000000007;
const int mod2 = 998244353;
const ld eps = 1e-9;
const int inf = ((1ll<<31ll)-1ll);
const int INF = 1ll * mod * mod;
const ld pi = acos(-1);
/// Prime Numbers:
// 2, 173, 179, 181, 197, 311, 331, 737, 1009, 2011, 2027, 3079, 4001, 10037, 10079, 20011, 20089;
// 100003, 100019, 100043, 200003, 200017, 1000003, 1000033, 1000037, 1000081;
// 2000003, 2000029, 2000039, 1000000007, 1000000021, 2000000099;
/// Functions:
#define lg2(x) 31 - __builtin_clz(x)
#define lgx(x,b) ( log(x) / log(b) )
/// Red-Black Tree Template ---------------------------------
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
//typedef tree < long long ,  null_type ,  less<long long> ,  rb_tree_tag ,  tree_order_statistics_node_update > ordered_set;
/// Quick Pow------------------------------------------------
int qpow(int b,int e){
    if( !e ) return 1;
    if( e & 1 ) return qpow(b,e-1) * b % mod;
    int pwur = qpow(b,e>>1);
    return pwur * pwur % mod;
}
int modinv(int x){ return qpow(x,mod-2); }
bool isprime(int x){
    for(int i=2; i*i<=x; i++)
        if( x % i == 0 )
            return false;
    return true;
}
/// My Code -------------------------------------------------



int32_t main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    cout.setf(ios::fixed); cout.precision(10);
    srand(time(NULL));

    //freopen("a.in","r",stdin);
    //freopen("a.in","w",stdout);

    vector<int> pr;
    for(int i=2; i<=50; i++){
        if( isprime(i) )
            pr.pb(i);
    }

    int n;
    cin >> n;

    vector<int> a(n+2);
    for(int i=1; i<=n; i++)
        cin >> a[i];

    int ans = -1;
    for(int i=0; i<(1<<(pr.size())); i++){
        int curr = 1;
        for(int j=0; j<pr.size(); j++){
            if( i & (1<<j) )
                curr *= pr[j];
        }
        bool can = 1;
        for(int j=1; j<=n; j++){
            if( __gcd( curr , a[j] ) == 1 )
                can = 0;
        }
        if( can ){
            if( ans == -1 ) ans = curr;
                else ans = min( ans , curr );
        }
    }

    cout << ans << '\n';

    return 0;
}

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

int main()
{
    int n;
    scanf("%d", &n);
    vector<long long> a(n);
    for (long long &x : a)
        scanf("%lld", &x);

    long long ans = LONG_LONG_MAX;
    vector<long long> nums = {2,
                              3,
                              5,
                              7,
                              11,
                              13,
                              17,
                              19,
                              23,
                              29,
                              31,
                              37,
                              41,
                              43,
                              47};
    int m = nums.size();
    function<void(int, long long)> f = [&](int k, long long h) {
        if (k == m)
        {
            for (long long x : a)
            {
                if (__gcd(x, h) == 1)
                    return;
            }
            ans = min(ans, h);
        }
        else
        {
            f(k + 1, h);
            f(k + 1, h * nums[k]);
        }
    };
    f(0, 1);
    printf("%lld", ans);
}
