Problem:
Score : 300 points

Problem Statement

You are given integers N and K. Find the number of triples (a,b,c) of positive integers not greater than N such that a+b,b+c and c+a are all multiples of K.
The order of a,b,c does matter, and some of them can be the same.

Constraints

1 \leq N,K \leq 2\times 10^5

N and K are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

Print the number of triples (a,b,c) of positive integers not greater than N such that a+b,b+c and c+a are all multiples of K.

Sample Input 1

3 2

Sample Output 1

9

(1,1,1),(1,1,3),(1,3,1),(1,3,3),(2,2,2),(3,1,1),(3,1,3),(3,3,1) and (3,3,3) satisfy the condition.

Sample Input 2

5 3

Sample Output 2

1

Sample Input 3

31415 9265

Sample Output 3

27

Sample Input 4

35897 932

Sample Output 4

114191

Solution in Rust (1.15.1) (judge verdict: Time Limit Exceeded)

fn main() {
    let mut string = String::new();
    std::io::stdin().read_line(&mut string).unwrap();
    let elms = string.split(" ").map(|elm| elm.trim().parse::<i64>().unwrap()).collect::<Vec<i64>>();
    let (N, K) = (elms[0], elms[1]);

    let mut res = 0;
    for a in 1..(N+1) {
        for b in 1..(N+1) {
            if (a + b) % K == 0 {
                for c in 1..(N+1) {
                    if (c + a) % K == 0 && (c + b) % K == 0 {
                        res += 1;
                    }
                }
            }
        }
    }

    println!("{}", res);
}