using AtCoderBeginnerContest153.Questions;
using AtCoderBeginnerContest153.Extensions;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace AtCoderBeginnerContest153.Questions
{
    // 復習
    public class QuestionF_Review : AtCoderQuestionBase
    {
        public override IEnumerable<object> Solve(TextReader inputStream)
        {
            var nda = inputStream.ReadIntArray();
            var n = nda[0];
            var d = nda[1];
            var a = nda[2];

            var monsters = new Monster[n];
            for (int i = 0; i < n; i++)
            {
                var xh = inputStream.ReadIntArray();
                monsters[i] = new Monster(xh[0], xh[1]);
            }

            Array.Sort(monsters);
            var blasts = new Queue<Blast>();

            long count = 0;
            long damage = 0;

            foreach (var monster in monsters)
            {
                while (blasts.Any() && blasts.Peek().MaxCoordinate < monster.Coordinate)
                {
                    damage -= blasts.Dequeue().Damage;
                }

                if (monster.HP - damage <= 0)
                {
                    continue;
                }

                var maxCoordinate = monster.Coordinate + 2 * d;
                var bomb = (int)Math.Ceiling((double)(monster.HP - damage) / a);
                var singleDamge = a * bomb;
                damage += singleDamge;
                count += bomb;
                blasts.Enqueue(new Blast(singleDamge, maxCoordinate));
            }

            yield return count;
        }

        private struct Monster : IComparable<Monster>
        {
            public int Coordinate { get; }
            public int HP { get; }

            public Monster(int position, int hp)
            {
                Coordinate = position;
                HP = hp;
            }

            public int CompareTo(Monster other) => Coordinate - other.Coordinate;

            public override string ToString() => $"X:{Coordinate}, HP:{HP}";
        }

        private struct Blast
        {
            public int MaxCoordinate { get; }
            public int Damage { get; }

            public Blast(int damage, int maxCoordinate)
            {
                Damage = damage;
                MaxCoordinate = maxCoordinate;
            }

            public override string ToString() => $"Damage:{Damage}, MaxCoordinate:{MaxCoordinate}";
        }
    }
}


namespace AtCoderBeginnerContest153
{
    class Program
    {
        static void Main(string[] args)
        {
            IAtCoderQuestion question = new QuestionF_Review();    // 問題に合わせて書き換え
            var answers = question.Solve(Console.In);
            foreach (var answer in answers)
            {
                Console.WriteLine(answer);
            }
        }
    }
}

#region Base Classes

namespace AtCoderBeginnerContest153.Questions
{

    public interface IAtCoderQuestion
    {
        IEnumerable<object> Solve(string input);
        IEnumerable<object> Solve(TextReader inputStream);
    }

    public abstract class AtCoderQuestionBase : IAtCoderQuestion
    {
        public IEnumerable<object> Solve(string input)
        {
            var stream = new MemoryStream(Encoding.Unicode.GetBytes(input));
            var reader = new StreamReader(stream, Encoding.Unicode);

            return Solve(reader);
        }

        public abstract IEnumerable<object> Solve(TextReader inputStream);
    }

}

#endregion

#region Extensions

namespace AtCoderBeginnerContest153.Extensions
{
    internal static class TextReaderExtensions
    {
        internal static int ReadInt(this TextReader reader) => int.Parse(ReadString(reader));
        internal static long ReadLong(this TextReader reader) => long.Parse(ReadString(reader));
        internal static double ReadDouble(this TextReader reader) => double.Parse(ReadString(reader));
        internal static string ReadString(this TextReader reader) => reader.ReadLine();

        internal static int[] ReadIntArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(int.Parse).ToArray();
        internal static long[] ReadLongArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(long.Parse).ToArray();
        internal static double[] ReadDoubleArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(double.Parse).ToArray();
        internal static string[] ReadStringArray(this TextReader reader, char separator = ' ') => reader.ReadLine().Split(separator);
    }
}

#endregion

Measured memory_bytes: 19452