import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static long largestValue(int[] A)
    {
        int max = 0,index;
        int B[] = new int[4];
        for(int i=0;i<4;i++)
        {
           max = A[0];
            index = 0;
            for(int j = 1;j<A.length;j++)
            {
                if(max<A[j])
                {
                    max = A[j];
                    index = j;
                }
            }
            B[i] = max;
            A[index] = Integer.MIN_VALUE;
        }
        int C[] = new int[6];
        int l=0;
        for(int j=0;j<4;j++)
        {
            for(int k=j+1;k<4;k++)
            {
                C[l++]=B[j]*B[k];
            }
        }
        int sum=0;
        for(int m=0;m<6;m++)
        {
         sum = sum+C[m];   
        }
        return sum;
        
            
       
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] A = new int[n];
        for(int A_i = 0; A_i < n; A_i++){
            A[A_i] = in.nextInt();
        }
        long result = largestValue(A);
        System.out.println(result);
        in.close();
    }
}