https://codeforces.com/contest/1165/problem/D

题解：给定的数组是答案的除1和本身以外所有因子，求答案

题解：贪心

答案=最大值*最小值

因子可能有多或者少；

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
ll ans,cnt,flag,temp,sum;
ll a[N];
char str;
struct node{};
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        ll maxl=-INF;
        ll minl=INF;
        for(int i=1;i<=n;i++){
            scanf("%I64d",&a[i]);
            maxl=max(a[i],maxl);
            minl=min(a[i],minl);
        }
        ans=maxl*minl;
        sort(a+1,a+n+1);
        int sqr=sqrt(ans);
        cnt=0;
        for(int i=2;i<=sqr;i++){
            if(ans%i==0){
                int x=lower_bound(a+1,a+n+1,ans/i)-a;
                int y=lower_bound(a+1,a+n+1,i)-a;
                //cout<<x<<endl;
                if(x>n||x<1||y>n||y<1||a[x]!=ans/i||a[y]!=i){
                    ans=-1;
                    break;
                }
                cnt++;
                if((ll)i*i!=ans){
                    cnt++;
                }
            }
        }
        cout<<(cnt==n?ans:-1)<<endl;
    }

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}