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 $0$.