#line 2 "/Users/noya2/Desktop/Noya2_library/template/template.hpp"
using namespace std;

#include<bits/stdc++.h>
#line 1 "/Users/noya2/Desktop/Noya2_library/template/inout_old.hpp"
namespace noya2 {

template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p){
    os << p.first << " " << p.second;
    return os;
}
template <typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &p){
    is >> p.first >> p.second;
    return is;
}

template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v){
    int s = (int)v.size();
    for (int i = 0; i < s; i++) os << (i ? " " : "") << v[i];
    return os;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &v){
    for (auto &x : v) is >> x;
    return is;
}

void in() {}
template <typename T, class... U>
void in(T &t, U &...u){
    cin >> t;
    in(u...);
}

void out() { cout << "\n"; }
template <typename T, class... U, char sep = ' '>
void out(const T &t, const U &...u){
    cout << t;
    if (sizeof...(u)) cout << sep;
    out(u...);
}

template<typename T>
void out(const vector<vector<T>> &vv){
    int s = (int)vv.size();
    for (int i = 0; i < s; i++) out(vv[i]);
}

struct IoSetup {
    IoSetup(){
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(15);
        cerr << fixed << setprecision(7);
    }
} iosetup_noya2;

} // namespace noya2
#line 1 "/Users/noya2/Desktop/Noya2_library/template/const.hpp"
namespace noya2{

const int iinf = 1'000'000'007;
const long long linf = 2'000'000'000'000'000'000LL;
const long long mod998 =  998244353;
const long long mod107 = 1000000007;
const long double pi = 3.14159265358979323;
const vector<int> dx = {0,1,0,-1,1,1,-1,-1};
const vector<int> dy = {1,0,-1,0,1,-1,-1,1};
const string ALP = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const string alp = "abcdefghijklmnopqrstuvwxyz";
const string NUM = "0123456789";

void yes(){ cout << "Yes\n"; }
void no(){ cout << "No\n"; }
void YES(){ cout << "YES\n"; }
void NO(){ cout << "NO\n"; }
void yn(bool t){ t ? yes() : no(); }
void YN(bool t){ t ? YES() : NO(); }

} // namespace noya2
#line 1 "/Users/noya2/Desktop/Noya2_library/template/utils.hpp"
namespace noya2{

unsigned long long inner_binary_gcd(unsigned long long a, unsigned long long b){
    if (a == 0 || b == 0) return a + b;
    int n = __builtin_ctzll(a); a >>= n;
    int m = __builtin_ctzll(b); b >>= m;
    while (a != b) {
        int mm = __builtin_ctzll(a - b);
        bool f = a > b;
        unsigned long long c = f ? a : b;
        b = f ? b : a;
        a = (c - b) >> mm;
    }
    return a << min(n, m);
}

template<typename T> T gcd_fast(T a, T b){ return static_cast<T>(inner_binary_gcd(abs(a),abs(b))); }

long long sqrt_fast(long long n) {
    if (n <= 0) return 0;
    long long x = sqrt(n);
    while ((x + 1) * (x + 1) <= n) x++;
    while (x * x > n) x--;
    return x;
}

template<typename T> T floor_div(const T n, const T d) {
    assert(d != 0);
    return n / d - static_cast<T>((n ^ d) < 0 && n % d != 0);
}

template<typename T> T ceil_div(const T n, const T d) {
    assert(d != 0);
    return n / d + static_cast<T>((n ^ d) >= 0 && n % d != 0);
}

template<typename T> void uniq(vector<T> &v){
    sort(v.begin(),v.end());
    v.erase(unique(v.begin(),v.end()),v.end());
}

template <typename T, typename U> inline bool chmin(T &x, U y) { return (y < x) ? (x = y, true) : false; }

template <typename T, typename U> inline bool chmax(T &x, U y) { return (x < y) ? (x = y, true) : false; }

template<typename T> inline bool range(T l, T x, T r){ return l <= x && x < r; }

} // namespace noya2
#line 8 "/Users/noya2/Desktop/Noya2_library/template/template.hpp"

#define rep(i,n) for (int i = 0; i < (int)(n); i++)
#define repp(i,m,n) for (int i = (m); i < (int)(n); i++)
#define reb(i,n) for (int i = (int)(n-1); i >= 0; i--)
#define all(v) (v).begin(),(v).end()

using ll = long long;
using ld = long double;
using uint = unsigned int;
using ull = unsigned long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using pil = pair<int,ll>;
using pli = pair<ll,int>;

namespace noya2{

/*　~ (. _________ . /)　*/

}

using namespace noya2;


#line 2 "c.cpp"

/*

struct Mo {
    int width;
    std::vector<int> left, right, order;

    Mo(int N = 1, int Q = 1): order(Q) {
        width = std::max<int>(1, 1.0 * N / std::max<double>(1.0, std::sqrt(Q * 2.0 / 3.0)));
        std::iota(begin(order), end(order), 0);
    }

    void insert(int l, int r) {
        left.emplace_back(l);
        right.emplace_back(r);
    }

    template <typename AL, typename AR, typename DL, typename DR, typename REM>
    void run(const AL& add_left, const AR& add_right, const DL& delete_left,
        const DR& delete_right, const REM& rem) {
        assert(left.size() == order.size());
        sort(begin(order), end(order), [&](int a, int b) {
            int ablock = left[a] / width, bblock = left[b] / width;
            if (ablock != bblock) return ablock < bblock;
            if (ablock & 1) return right[a] < right[b];
            return right[a] > right[b];
            });
        int nl = 0, nr = 0;
        for (auto idx : order) {
            while (nl > left[idx]) add_left(--nl);
            while (nr < right[idx]) add_right(nr++);
            while (nl < left[idx]) delete_left(nl++);
            while (nr > right[idx]) delete_right(--nr);
            rem(idx);
        }
    }
};

*/

#line 2 "/Users/noya2/Desktop/Noya2_library/misc/rng.hpp"

#line 4 "/Users/noya2/Desktop/Noya2_library/misc/rng.hpp"

namespace noya2 {

// [0, 2^64 - 1)
ull rng() {
  static ull _x = 88172645463325252UL;
  return _x ^= _x << 7, _x ^= _x >> 9;
}

// [l, r]
ll rng(ll l, ll r) {
  assert(l <= r);
  return l + rng() % ull(r - l + 1);
}

// [l, r)
ll randint(ll l, ll r) {
  assert(l < r);
  return l + rng() % ull(r - l);
}

// [0.0, 1.0)
ld rnd() { return rng() * 5.42101086242752217004e-20; }
// [l, r)
ld rnd(ld l, ld r) {
  assert(l < r);
  return l + rnd() * (r - l);
}

} // namespace noya2
#line 43 "c.cpp"

void solve(){
    ll n, l; in(n,l);
    vector<pll> xys(n); in(xys);
    // rep(i,n){
    //     xys[i].first = randint(0,l);
    //     xys[i].second = randint(0,l);
    // }
    ll width = max<ll>(1, 1.0 * l / max<double>(1.0, sqrt(n * 2.0 / 3.0)));
    vector<int> order(n); iota(all(order),0);
    sort(all(order),[&](int a, int b){
        ll ablock = xys[a].first / width, bblock = xys[b].first / width;
        if (ablock != bblock) return ablock < bblock;
        ll ra = xys[a].second, rb = xys[b].second;
        if (ablock & 1) return ra < rb;
        return ra > rb;
    });
    auto dist = [&](int i, int j){
        ll x = abs(xys[i].first - xys[j].first);
        ll y = abs(xys[i].second - xys[j].second);
        return x + y;
    };
    out(n);
    for (int i : order){
        out(xys[i]);
    }
    ll ans = dist(order[0],order[n-1]);
    rep(i,n-1) ans += dist(order[i],order[i+1]);
    assert(ans <= 1000*l);
}

int main(){
    int t = 1; in(t);
    while (t--) { solve(); }
}