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

public class Solution {
    static class struct {
        private long fval=0;
        private long Sval =0;
        
        struct ( long j , long h ){
            this.fval=j;
            this.Sval=h;
        }
    }

    static long largestValue(int[] A) {
        struct [] ff = new struct[(int ) Math.pow(A.length,A.length)];
        // Return the largest value of any of A's nonempty subarrays.
        int i =0;
        for (int k=0;k<A.length;k++){
            for (int j=k;j<A.length;j++){
                if (k!=j)
                ff [i] = new struct(A[k],A[j]);
                i++;
            }
        }
        long max =0;
        for (int j=0;j<ff.length;j++){
           if (max < ff[j].Sval*ff[j].fval) max = ff[j].Sval*ff[j].fval;
        }
        return max ;
    }

    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();
    }
}