#include<bits/stdc++.h>
#include<fstream>

using namespace std;
int main ()
{
  std::ifstream in("maxsum.in");
    std::cin.rdbuf(in.rdbuf());
    std::ofstream out("maxsum.out");
    std::cout.rdbuf(out.rdbuf());
unsigned long long n;
cin>>n;
unsigned long long a[n+1],s=0;
for(int i=0;i<n;i++)
{
    cin>>a[i];
}
sort(a,a+n);
for(int i=0;i<n-2;++i)
{
    s+=a[i]*a[i+2];
}
s+=a[0]*a[1]+a[n-2]*a[n-1];
cout<<s<<endl;
    return 0;
}