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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function Main(input){
    var input = input.split("\n");
    var a = input[1].split(" ").sort();
    var result = [];
    var temp = 0;

    for(var i = input[0] - 1; i > 0; i--){
        if(a.indexOf(a[i]) !== i && temp !== a[i]){
            temp = a[i];
            result.push(a[i]);
        }
        if(result.length === 2){
            break;
        }
    }

    if(result.length === 0){
        console.log(0)
    }else{
        console.log('%d', result[0] * result[1]);
    }
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));