#include <bits/stdc++.h>

using namespace std;

long maximumValue(int *a,int n) {
    int res=0,i,j,a1,b,max=0,sum=0,gcd=0,max1=0;
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
           if(i==j)
           {
               max=a[i];
               gcd=a[i];
               sum=a[i];
           }
            else
            {
            a1=a[i];b=a[j];
            gcd=__gcd(a1, b);
                if(gcd<0)
                {
                    gcd=-1*gcd;
                }
            sum=a1+b;
             if(a1>b)
             {
                 max=a1;
             }
                else
                {
                    max=b;
                }
                res=gcd*(sum-max);
                //printf("%d\n",res);
            }
   

        }
        if(max1<res)
        {
            max1=res;
        }
    }
    return max1/2;
    // Return the maximum value of f among all subsegments [l..r].
}

int main() {
    int n;
    cin >> n;
    int a[n];
    for(int a_i = 0; a_i < n; a_i++){
       cin >> a[a_i];
    }
    long result = maximumValue(a,n);
    cout << result << endl;
    return 0;
}