import java.io.*;
import java.util.*;

class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader bu=new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb=new StringBuilder();
        int n=Integer.parseInt(bu.readLine());
        int i; long a;

        String s[]=bu.readLine().split(" ");
        TreeMap<Long,Integer> tm=new TreeMap<>();
        for(i=0;i<n;i++)
        {
            a=Integer.parseInt(s[i]);
            tm.put(a,tm.getOrDefault(a,0)+1);
        }

        long ans=-1;
        boolean alice=true;
        while(true)
        {
            long lo=tm.higherKey(-1l);
            if(tm.size()==1 && tm.get(lo)==1)
            {
                ans=lo;
                break;
            }

            if(alice)
            {
                remove(tm,lo);
                long lo2=tm.higherKey(lo-1);
                remove(tm,lo2);
                tm.put(lo*lo2,tm.getOrDefault(lo*lo2,0)+1);
            }
            else
            {
                long hi=tm.lowerKey(Long.MAX_VALUE);
                remove(tm,hi);
                long hi2=tm.lowerKey(hi+1);
                remove(tm,hi2);
                tm.put(1l,tm.getOrDefault(1l,0)+1);
            }

            alice=!alice;
        }
        System.out.println(ans);
    }

    static void remove(TreeMap<Long,Integer> tm,long x)
    {
        int v=tm.get(x);
        if(v==1) tm.remove(x);
        else tm.put(x,v-1);
    }
}