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;
        int index=0;
        for(int i=0; i<A.length;i++){
            if(A[i]>max){
                max=A[i];
                index=i;   
            }
        }
        int[] a=new int[4];
        for(int j=index; j<4;j++){
            for(int k=0;k<4;k++){
                a[k]=A[j];
                
            }
        }
            
         int b=a[0]*a[1];
       int c=a[2]*a[3];
        return b+c;
        
        
        
        
        // Return the largest value of any of A's nonempty subarrays.
        
        
    }

    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();
    }
}