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
num=raw_input()
tmp=map(int, raw_input().split(" "))
tmp.sort()
tmp.reverse()
oldnum=0
arr=[]
flag=0
out=0
for i in range(len(tmp)-1):
    if tmp[i]==tmp[i+1] and flag==0:
            arr.append(tmp[i])
            flag=1
    else:
        flag=0
    if len(arr)==2:
        out=arr[0]*arr[1]
        break
    try:
        if tmp[i]==tmp[i+1] and tmp[i]==tmp[i+2] and tmp[i]==tmp[i+3]:
            out=tmp[i]**2
            break
    except:
        pass
print out