#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <tuple>

using namespace std;

void solve (int N, int L, vector<pair<int, int>>& points) {
    // 最適解は求められないはず -> Moの巡回順でやってみる
    int width = (int) (L / sqrt(N));

    vector<tuple<int, int, int>> query(N);
    for (int i = 0; i < N; i++) {
        query[i] = make_tuple(points[i].first, points[i].second, points[i].first / width);
    }

    sort(query.begin(), query.end(),
            [](tuple<int, int, int>& x, tuple<int, int, int>& y) {
            if (get<2>(x) != get<2>(y)) return get<2>(x) < get<2>(y);
            return get<1>(x) < get<1>(y);
            });

    cout << N << "\n";
    for (auto& q : query) {
        cout << get<0>(q) << " " << get<1>(q) << "\n";
    }
}

int main () {
    int T; cin >> T;
    for (int t = 0; t < T; t++) {
        int N, L; cin >> N >> L;
        vector<pair<int, int>> points(N);
        for (int i = 0; i < N; i++) {
            int X, Y; cin >> X >> Y;
            points[i] = make_pair(X, Y);
        }

        solve(N, L, points);
    }
}