import java.awt.*;
import java.awt.geom.*;
import java.io.*;
import java.util.*;
class Main {
    static int MAX_N = 131072 * 2;
    static int[] dat = new int[MAX_N];
    static int n;
 
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        int d = sc.nextInt();
        Data[] data = new Data[n];
        for(int i = 0; i < n; i++) {
            data[i] = new Data(sc.nextInt(),sc.nextInt(),sc.nextInt());
        }
        Arrays.sort(data);
         
        SegTree xmin = new SegTree(n);
        SegTreeM xmax = new SegTreeM(n);
        SegTree ymin = new SegTree(n);
        SegTreeM ymax = new SegTreeM(n);
         
        for(int i = 0; i < n; i++) {
            xmin.update(i, data[i].x);
            xmax.update(i, data[i].x);
            ymin.update(i, data[i].y);
            ymax.update(i, data[i].y);
        }
        long max = 0;
        int r = 0;
        for(int i = 0; i < n; i++) {
            while(r+1 < n && data[i].b + d >= data[r+1].b) {
                r++;
            }
            long sum = 0;
            if(i != r) {
            sum = (long)(xmax.query(i, r+1) - xmin.query(i, r+1))*(ymax.query(i, r+1) - ymin.query(i, r+1));
            }
            else {
                sum = 0;
            }
            max = Math.max(sum, max);
        }
         
         
        System.out.println(max);
    }
     
    static class SegTreeM {
        int n, n_, m;
        int[] node;
         
        public SegTreeM(int n) {
            this.n = n;
            this.n_ = Integer.highestOneBit(Math.max(n-1,1) << 1);
            this.m = 2*n_- 1;
            this.node = new int[m];
            Arrays.fill(node, Integer.MIN_VALUE);
        }
         
        void update(int x, int a) {
            x += n_ -1;
            node[x] = a;
            while(x > 0) {
                x = (x-1)/2;
                node[x] = Math.max(node[2*x+1], node[2*x+2]);
            }
        }
         
        int query(int l, int r) {
            return query(l,r,0,n_,0);
        }
  
        private int query(int l, int r, int cl, int cr, int cur) {
            if (l <= cl && cr <= r) {
                return node[cur];
            }else {
                int ret = Integer.MIN_VALUE;
                int mid = (cl+cr)/2;
                if (cl < r && l < mid)
                    ret = Math.max(ret,query(l,r,cl,mid,2*cur+1));
                if (mid < r && l < cr)
                    ret = Math.max(ret,query(l,r,mid,cr,2*cur+2));
                return ret;
            }
        }
         
         
    }
     
     
     
    static class SegTree {
        int n, n_, m;
        int[] node;
         
        public SegTree(int n) {
            this.n = n;
            this.n_ = Integer.highestOneBit(Math.max(n-1,1) << 1);
            this.m = 2*n_- 1;
            this.node = new int[m];
            Arrays.fill(node, Integer.MAX_VALUE);
        }
         
        void update(int x, int a) {
            x += n_ -1;
            node[x] = a;
            while(x > 0) {
                x = (x-1)/2;
                node[x] = Math.min(node[2*x+1], node[2*x+2]);
            }
        }
         
        int query(int l, int r) {
            return query(l,r,0,n_,0);
        }
  
        private int query(int l, int r, int cl, int cr, int cur) {
            if (l <= cl && cr <= r) {
                return node[cur];
            }else {
                int ret = Integer.MAX_VALUE;
                int mid = (cl+cr)/2;
                if (cl < r && l < mid)
                    ret = Math.min(ret,query(l,r,cl,mid,2*cur+1));
                if (mid < r && l < cr)
                    ret = Math.min(ret,query(l,r,mid,cr,2*cur+2));
                return ret;
            }
        }
         
         
    }
     
     
     
    static class Data implements Comparable<Data> {
        int x;
        int y;
        int b;
         
        Data(int a , int c, int d) {
            x = a;
            y = c;
            b = d;
        }
        @Override
        public int compareTo(Data o) {
            return this.b - o.b;
        }
    }
     
}


Measured memory_bytes: 174412