#include<cstdio>

 #include<cmath>

 #include<algorithm>

 using namespace std;

 typedef long long LL;

 bool ans[][];

 LL a[],n,sum;

 double p,anss;

 int main()

 {

     LL i,j,k,x,y,z;

     scanf("%lld",&n);

     for(i=;i<=n;i++)

     {

         scanf("%lld",&a[i]);

         sum+=a[i];

     }

     ans[][]=;

     for(i=;i<=n;i++)

         for(j=sum;j>=;j--)

             for(k=sum;k>=;k--)

             {

                 if(j>=a[i])

                     ans[j][k]|=ans[j-a[i]][k];

                 if(k>=a[i])

                     ans[j][k]|=ans[j][k-a[i]];

             }

     for(x=;x<=sum;x++)

         for(y=x;y<=sum-x-;y++)

         {

             if(!ans[x][y])    continue;

             z=sum-x-y;

             if(y>z)    break;

             if(x+y<=z) continue;

             p=(double)(x+y+z)/2.0;

             anss=max(anss,sqrt(p*(p-x)*(p-y)*(p-z)));

         }

     if(anss!=0.0)

         printf("%lld",(long long)(anss*(double)));

     else

         printf("-1");

     return ;

 }