2491 - Divide Players Into Teams of Equal Skill\.

Medium

You are given a positive integer array skill of even length n where skill[i] denotes the skill of the <code>i^th</code> player. Divide the players into n / 2 teams of size 2 such that the total skill of each team is equal.

The chemistry of a team is equal to the product of the skills of the players on that team.

Return the sum of the chemistry of all the teams, or return -1 if there is no way to divide the players into teams such that the total skill of each team is equal.

Example 1:

Input: skill = 3,2,5,1,3,4

Output: 22

Explanation: Divide the players into the following teams: (1, 5), (2, 4), (3, 3), where each team has a total skill of 6. The sum of the chemistry of all the teams is: 1 \* 5 + 2 \* 4 + 3 \* 3 = 5 + 8 + 9 = 22.

Example 2:

Input: skill = 3,4

Output: 12

Explanation: The two players form a team with a total skill of 7. The chemistry of the team is 3 \* 4 = 12.

Example 3:

Input: skill = 1,1,2,3

Output: -1

Explanation: There is no way to divide the players into teams such that the total skill of each team is equal.

Constraints:

• <code>2 <= skill.length <= 10⁵</code>

• skill.length is even.

• 1 <= skill[i] <= 1000