#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <utility>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <functional>

using namespace std;

#define fst first
#define scd second
#define PB push_back
#define MP make_pair
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define omajinai ios::sync_with_stdio(false);cin.tie(0)
#define rep(i,x) for(int i=0;i<(int)(x);++i)
#define rep1(i,x) for(int i=1;i<=(int)(x);++i)

typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pii;
typedef vector<pii> vpii;

template<typename T>T& max(T&a,T&b){if(a>=b)return a;return b;}
template<typename T>T& min(T&a,T&b){if(a<b)return a;return b;}
template<typename T>bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<typename T>bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<typename T>T get(){T a;cin>>a;return a;}
template<typename T>T rev(T a){reverse(all(a));return a;}
template<typename T>vector<T>&sort(vector<T>&a){sort(all(a));return a;}

const int inf = 1e9;
const ll linf = 3e18;
const double eps = 1e-9;

struct SegTree { // ??????min,max
	int n;
	vector<int> Max;
	vector<int> Min;

	void init(int n_)
	{
		n = 1;
		while (n < n_) n *= 2;

		Max.resize(2 * n);
		Min.resize(2 * n);

		for (int i = 0; i < 2 * n - 1; ++i) {
			Max[i] = -inf;
			Min[i] = inf;
		}
	}

	void min_update(int idx, int val)
	{
		idx += n - 1;
		Min[idx] = val;

		while (idx > 0) {
			idx = (idx - 1) / 2;
			Min[idx] = min(Min[idx * 2 + 1], Min[idx * 2 + 2]);
		}
	}

	void max_update(int idx, int val)
	{
		idx += n - 1;
		Max[idx] = val;

		while (idx > 0) {
			idx = (idx - 1) / 2;
			Max[idx] = max(Max[idx * 2 + 1], Max[idx * 2 + 2]);
		}
	}

	int get_min(int a, int b, int k = 0, int l = 0, int r = -1) // [a, b)???min
	{
		if (r == -1) r = n;

		if (r <= a || b <= l) return inf;

		if (a <= l && r <= b) return Min[k];

		int vl = get_min(a, b, k * 2 + 1, l, (l + r) / 2);
		int vr = get_min(a, b, k * 2 + 2, (l + r) / 2, r);

		return min(vl, vr);
	}

	int get_max(int a, int b, int k = 0, int l = 0, int r = -1) // [a, b)???max
	{
		if (r == -1) r = n;

		if (r <= a || b <= l) return -inf;

		if (a <= l && r <= b) return Max[k];

		int vl = get_max(a, b, k * 2 + 1, l, (l + r) / 2);
		int vr = get_max(a, b, k * 2 + 2, (l + r) / 2, r);

		return max(vl, vr);
	}
};

int X[200020], Y[200020];

signed main()
{
	int N, d; scanf("%d%d", &N, &d);

	SegTree x_seg, y_seg;

	x_seg.init(N), y_seg.init(N);

	vpii hoge;

	rep(i, N) {
		int x, y, b; scanf("%d%d%d", &x, &y, &b);
		X[i] = x, Y[i] = y;

		hoge.PB(pii(b, i));
	}

	sort(all(hoge));

	rep(i, N) {
		x_seg.min_update(i, X[hoge[i].scd]);
		x_seg.max_update(i, X[hoge[i].scd]);

		y_seg.min_update(i, Y[hoge[i].scd]);
		y_seg.max_update(i, Y[hoge[i].scd]);
	}

	ll ans = -inf;

	rep(i, N) {
		if (i > 0 && hoge[i].fst == hoge[i - 1].fst) continue;

		int b = hoge[i].fst;

		int idx = upper_bound(all(hoge), pii(b + d, inf)) - hoge.begin();

		int min_x = x_seg.get_min(i, idx);
		int max_x = x_seg.get_max(i, idx);

		int min_y = y_seg.get_min(i, idx);
		int max_y = y_seg.get_max(i, idx);

		ans = max(ans, 1ll * (max_x - min_x) * (max_y - min_y));
	}

    printf("%lld\n", ans);
}

Measured memory_bytes: 12580