Problem Statement

You are given $a sequence A=(A_1,A_2,\ldots,A_N)$ of length N consisting of non-negative integers.
Determine if there is an even number represented as the sum of two different elements of A. If it exists, find the maximum such number.

Input

The input is given from Standard Input in the following format:
N
$A_1 A_2 \ldots A_N$

Output

Print -1 if there is no even number represented as the sum of two different elements of A.
If such an even number exists, print the maximum such number.

Constraints

• $2\leq N \leq 2\times 10^5$
• $0\leq A_i\leq 10^9$
• The elements of A are distinct.
• All values in the input are integers.

Sample Input 1

3
2 3 4

Sample Output 1

6

The values represented as the sum of two distinct elements of A are 5, 6, and 7. We have an even number here, and the maximum is 6.

Sample Input 2

2
1 0

Sample Output 2

-1

The value represented as the sum of two distinct elements of A is 1. We have no even number here, so -1 should be printed.

见题面 Input 部分

见题面 Output 部分