My solution in c# passed all the test cases using System; using System.Collections.Generic; using System.IO; using System.Linq; class Solution {

static void Main(String[] args) {
    string[] tokens_n = Console.ReadLine().Split(' ');
    int n = Convert.ToInt32(tokens_n[0]);
    int k = Convert.ToInt32(tokens_n[1]);
    string[] a_temp = Console.ReadLine().Split(' ');
    int[] a = Array.ConvertAll(a_temp,Int32.Parse);
    int count=0;
    for(int i=0; i<n-1; i++)
    {           
        for(int j=i+1; j<n; j++)
        {
            if((a[i]+a[j])%k==0)
            {
                count=count+1;
            }
        }
    }
    Console.WriteLine(count);

}

}