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.

Examples

Input

6
3 1 2 4 2 1


Output

2


Input

4
1 2 3 4


Output

0


Input

10
3 3 3 3 4 4 4 5 5 5


Output

20
N=int(raw_input())
A=[int(x) for x in raw_input().split()]
 
used=dict()
for a in A:
    if a in used:
        used[a] += 1
    else:
        used[a]=1

B=[]
for a in used:
    if used[a]>=4:
        B.append(a)
        B.append(a)
    elif used[a]>=2:
        B.append(a)

if len(B)<2:
    print 0
else:
    B.sort(reverse=True)
    print B[0]*B[1]