Problem:
Score : 300 points

Problem Statement

We have N sticks with negligible thickness.
The length of the i-th stick is A_i.

Snuke wants to select four different sticks from these sticks and form a rectangle (including a square), using the sticks as its sides.
Find the maximum possible area of the rectangle.

Constraints

4 \leq N \leq 10^5

1 \leq A_i \leq 10^9

A_i is an integer.

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_N

Output

Print the maximum possible area of the rectangle.
If no rectangle can be formed, print 0.

Sample Input 1

6
3 1 2 4 2 1

Sample Output 1

2

1 \times 2 rectangle can be formed.

Sample Input 2

4
1 2 3 4

Sample Output 2

0

No rectangle can be formed.

Sample Input 3

10
3 3 3 3 4 4 4 5 5 5

Sample Output 3

20

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)


import java.util.Scanner;
import java.util.Arrays;

class Main{
        public static void main(String[] args){
                Scanner scanner=new Scanner(System.in);
                int n=scanner.nextInt();
                int[] a=new int[n];
                for(int i=0;i<n;i++){
                        a[i]=scanner.nextInt();
                }
                Arrays.sort(a);
                int j=a[n-1];
                int k=0;
                int[] h=new int[2];
                for(int i=1;i<n;i++){
                        if(a[n-1-i]==j){
                                i++;
                                h[k]=j;
                                k++;
                                if(k==2){
                                        System.out.println(h[0]*h[1]);
                                        return;
                                }
                        }
                        if(i>=n){
                                break;
                        }
                        j=a[n-1-i];
                }
                System.out.println(0);
        }
}