using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Text;
//using static CompLib.CompLib;
//using DataStructure;

namespace atcoder
{

    class Program
    {
        const int intMax = 1000000000;
        const long longMax = 2000000000000000000;
        static void Main(string[] args)
        {
            var NVC = Console.ReadLine().Trim().Split().Select(int.Parse).ToArray();
            int N = NVC[0];
            int V = NVC[1];
            int C = NVC[2];
            var items = new (int, int)[2 * N];
            for (int i = 0; i < 2 * N; i++)
            {
                if (i % 2 == 0)
                {
                    var read = Console.ReadLine().Trim().Split().Select(int.Parse).ToArray();
                    items[i] = (read[0], read[1] + C);
                }
                else
                {
                    items[i] = (items[i - 1].Item1, items[i - 1].Item2 - C);
                }
            }
            var dp = new int[2 * N + 1, V + 1];
            for (int i = 0; i < 2 * N; i++)
            {
                for (int j = 0; j <= V; j++)
                {
                    if (i >= 1)
                        dp[i, j] = Math.Max(dp[i, j], dp[i - 1, j]);
                    if (i % 2 == 0)
                    {
                        if (j - items[i].Item1 >= 0)
                        {
                            if (i > 0)
                                dp[i, j] = Math.Max(dp[i, j], dp[i - 1, j - items[i].Item1] + items[i].Item2);
                            else
                            {
                                dp[i, j] = items[i].Item2;
                            }
                        }

                    }
                    else
                    {
                        if (j - items[i].Item1 >= 0)
                            dp[i, j] = Math.Max(dp[i, j], dp[i, j - items[i].Item1] + items[i].Item2);
                    }
                }
            }
            long ans = 0;
            for (int i = 0; i <= V; i++)
            {
                ans = Math.Max(ans, dp[2 * N - 1, i]);
            }
            Console.WriteLine(ans);
        }
    }
}