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Codeforces
Medium
Combinatorics
Bit Manipulation
Math
Team
Count how many teams of 3 students can be formed such that the total skill level is even.
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Problem Statement
You are given the skill levels of students. Count the number of different teams of exactly 3 students whose combined skill is even.
A team is identified only by the chosen 3 students, so the order does not matter.
The task is to determine how many such teams can be formed.
Input Format
- The first line contains an integer .
- The second line contains integers representing the skill values.
Output Format
Print a single integer — the number of 3-person teams with even total skill.
Constraints
- Skill values fit in standard 32-bit signed integers.
- The answer may be large; use 64-bit integer arithmetic.
Examples
Sample cases returned by the problem API.
Example 1
Input
5 1 2 3 4 5
Output
3
Explanation
The valid teams are {1,2,3}, {1,4,5}, and {2,3,5}. Each has an even sum.
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