using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace task1
{
    class Tree : IComparable<Tree>
    {
        public int x;
        public int h;

        public Tree(int x, int h)
        {
            this.x = x;
            this.h = h;
        }

        public int CompareTo(Tree other)
        {
            return this.x.CompareTo(other.x);
        }
    }

    class Node
    {
        public int i;
        public int d;

        public Node(int i, int d)
        {
            this.i = i;
            this.d = d;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var line = Console.ReadLine().Split(' ');

            int n = int.Parse(line[0]);
            int mj = int.Parse(line[1]);
            int mh = int.Parse(line[2]);

            var trees = new Tree[n];
            for (int i = 0; i < n; i++)
            {
                line = Console.ReadLine().Split(' ');
                trees[i] = new Tree(int.Parse(line[0]), int.Parse(line[1]));
            }

            Array.Sort(trees);

            var visited = new bool[n];

            var q = new Queue<Node>();

            visited[0] = true;

            q.Enqueue(new Node(0, 0));
            while (q.Count != 0)
            {
                var p = q.Dequeue();

                for (int i = p.i + 1; i < n; i++)
                {
                    if (visited[i] == true)
                    {
                        continue;
                    }

                    if (Math.Abs(trees[p.i].x - trees[i].x) >= mj)
                    {
                        break;
                    }

                    if (Math.Abs(trees[p.i].h - trees[i].h) >= mh)
                    {
                        continue;
                    }

                    if (i == n - 1)
                    {
                        Console.WriteLine(p.d + 1);
                        return;
                    }
                    q.Enqueue(new Node(i, p.d + 1));
                    visited[i] = true;
                }
            }
            Console.WriteLine(-1);

        }
    }
}