#include <bits/stdc++.h>

//{ START
using namespace std;
#define int int64_t
#define rep(i, a, n) for (int i = (a); i < (n); ++i)
#define reps(i, a, n) for (int i = (n - 1); i > (a - 1); --i)
#define arep(i, x) for (auto &&i : (x))
#define irep(i, x) for (auto i = (x).begin(); i != (x).end(); ++i)
#define rirep(i, x) for (auto i = (x).rbegin(); i != (x).rend(); ++i)
//降順はgreater<T>()
#define all(x) (x).begin(), (x).end()
#define rv(s) reverse((s).begin(), (s).end())
// gcd lcmはそのままok
#define gcd(a, b) __gcd(a, b)
#define bits(n) (1LL << (n))
#define pcnt(x) __builtin_popcountll(x)
//配列内等要素削除
#define Unique(x) (x).erase(unique((x).begin(), (x).end()), (x).end())
#define Fixed(n) fixed << setprecision(n)
//総和
#define sowa(n) (((n) * ((n) + 1)) / 2)
#define updiv(a, b) ((a + b - 1) / b)
#define cauto const auto &
using P = pair<int, int>;
using Graph = vector<vector<P>>;
template <class T>  //昇順
using min_heap = priority_queue<T, vector<T>, greater<T>>;
template <class T>  //降順
using max_heap = priority_queue<T>;
template <class A, class B>
using umap = unordered_map<A, B>;
template <class A>
using uset = unordered_set<A>;
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {  //多次元初期化
  std::fill((T *)array, (T *)(array + N), val);
}
template <class A, class B>
bool chmax(A &a, const B &b) {  //最大値更新 返り値はbool
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class A, class B>
bool chmin(A &a, const B &b) {  //最小値更新 返り値はbool
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, 1, 1, -1, -1};
constexpr int INF = 0x3f3f3f3f;
constexpr int LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr int mod1 = 1e9 + 7;
constexpr int mod2 = 998244353;
//} END

template <typename Monoid>
struct SegmentTree {
  using F = function<Monoid(Monoid, Monoid)>;

  int sz;
  vector<Monoid> seg;

  const F f;
  const Monoid M1;

  SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1) {
    sz = 1;
    while (sz < n) sz <<= 1;
    seg.assign(2 * sz, M1);
  }

  void set(int k, const Monoid &x) { seg[k + sz] = x; }

  void build() {
    for (int k = sz - 1; k > 0; k--) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  void update(int k, const Monoid &x) {
    k += sz;
    seg[k] = x;
    while (k >>= 1) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  Monoid query(int a, int b) {
    Monoid L = M1, R = M1;
    for (a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if (a & 1) L = f(L, seg[a++]);
      if (b & 1) R = f(seg[--b], R);
    }
    return f(L, R);
  }

  Monoid operator[](const int &k) const { return seg[k + sz]; }

  template <typename C>
  int find_subtree(int a, const C &check, Monoid &M, bool type) {
    while (a < sz) {
      Monoid nxt = type ? f(seg[2 * a + type], M) : f(M, seg[2 * a + type]);
      if (check(nxt))
        a = 2 * a + type;
      else
        M = nxt, a = 2 * a + 1 - type;
    }
    return a - sz;
  }

  template <typename C>
  int find_first(int a, const C &check) {
    Monoid L = M1;
    if (a <= 0) {
      if (check(f(L, seg[1]))) return find_subtree(1, check, L, false);
      return -1;
    }
    int b = sz;
    for (a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if (a & 1) {
        Monoid nxt = f(L, seg[a]);
        if (check(nxt)) return find_subtree(a, check, L, false);
        L = nxt;
        ++a;
      }
    }
    return -1;
  }

  template <typename C>
  int find_last(int b, const C &check) {
    Monoid R = M1;
    if (b >= sz) {
      if (check(f(seg[1], R))) return find_subtree(1, check, R, true);
      return -1;
    }
    int a = sz;
    for (b += sz; a < b; a >>= 1, b >>= 1) {
      if (b & 1) {
        Monoid nxt = f(seg[--b], R);
        if (check(nxt)) return find_subtree(b, check, R, true);
        R = nxt;
      }
    }
    return -1;
  }
};

signed main(void) {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  int n, d;
  cin >> n >> d;
  vector<tuple<int, int, int>> star;
  auto maxf = [](int a, int b) { return max(a, b); };
  auto minf = [](int a, int b) { return min(a, b); };

  rep(i, 0, n) {
    int a, b, c;
    cin >> a >> b >> c;
    star.emplace_back(c, a, b);
  }
  sort(all(star));

  SegmentTree<int> maxx(n, maxf, 0);
  SegmentTree<int> minx(n, minf, LINF);
  SegmentTree<int> maxy(n, maxf, 0);
  SegmentTree<int> miny(n, minf, LINF);

  vector<int> v(n);
  rep(i, 0, n) {
    int bi, xi, yi;
    tie(bi, xi, yi) = star[i];
    v[i] = bi;
    maxx.set(i, xi);
    minx.set(i, xi);
    maxy.set(i, yi);
    miny.set(i, yi);
  }
  maxx.build();
  minx.build();
  maxy.build();
  miny.build();

  int ans = 0;
  rep(i, 0, n) {
    int key = v[i] + d;
    int r = distance(v.begin(), upper_bound(all(v), key));
    int nowx = maxx.query(i, r) - minx.query(i, r);
    int nowy = maxy.query(i, r) - miny.query(i, r);
    chmax(ans, (nowx * nowy));
  }
  cout << ans << '\n';
  return 0;
}


Measured memory_bytes: 25456