absolute.cpp

//{ Driver Code Starts
#include <bits/stdc++.h>
using namespace std;


// } Driver Code Ends
//User function Template for C++

class Solution {
  public:
    long long countPairs(int n, int arr[], int k) {
        // code here
        long long res=0;
        for(int i=0;i<n;i++){
            arr[i] = (arr[i]%k);
        }
        unordered_map<int,int> mp;
        for(int i=0;i<n;i++) mp[arr[i]]++;
        for(int i=0;i<k;i++){
           res += (mp[i]*(mp[i]-1))/2;
        }
        return res;
    }
};

//{ Driver Code Starts.


int main() {
    int t;
    cin >> t;
    while (t--) {
        int n,k;
        cin>>n;
        
        int arr[n];
        for(int i=0; i<n; i++)
            cin>>arr[i];
        
        cin>>k;

        Solution ob;
        cout << ob.countPairs(n,arr,k) << endl;
    }
    return 0;
}
// } Driver Code Ends