//Lecu Marina 322CB
// TEMA 1 - Problema 2

#include <stdio.h>
#include <stdlib.h>
//#include <conio.h>
#include <algorithm>
using namespace std;
#include <map>
using namespace std;

typedef struct
{
    unsigned int nmax,nluate;
} Nivel;

typedef struct
{
    unsigned int h,g;
} TGutuie;

bool compg(const TGutuie &g1,const TGutuie &g2)
{
    return g1.g > g2.g;
}

bool comph(const map<unsigned int,Nivel>::iterator it1,const map<unsigned int,Nivel>::iterator it2)
{
    return it1->first > it2->first;
}

int main()
{
    unsigned int N,H,U,G=0,i,ntotal,hmin;
    short c=1;
    FILE *in,*out;
    TGutuie* gutui;
    map<unsigned int,Nivel> nivele;
    map<unsigned int,Nivel>::iterator it,it2;

    Nivel niv;
    niv.nluate=0;
    in=fopen("gutui.in","r");
    out=fopen("gutui.out","w");
    
    fscanf(in,"%u %u %u",&N,&H,&U);                 //citire N,H,U                
    gutui = (TGutuie*) malloc(N*sizeof(TGutuie));   //alocare vector gutui
    //citire inaltimi si greutati gutui
    for(i=0; i<N; i++)
        {
            fscanf(in,"%u %u",&(gutui[i].h),(&gutui[i].g));
            if(gutui[i].h % U != 0)
                gutui[i].h = gutui[i].h - gutui[i].h % U + U;
            niv.nmax = (H - gutui[i].h)/U +1;
            //printf("%u: %u \n",gutui[i].h,niv.nmax);
            nivele[gutui[i].h]=niv;
            if(c)
            {
                hmin=gutui[i].h;
                c=0;
            }
            else if(hmin > gutui[i].h)
                    hmin = gutui[i].h;
        }
        
    sort(gutui,gutui+N,compg);                   //sortare in ordine descrescatoare dupa greutate
    ntotal = (H - hmin)/U +1;                    //nr total de gutui care pot fi culese
    for(i=0; i < N; i++)
    {
        if(ntotal==0) break;                    //am cules toate gutuile pe care le puteam culege
        it=nivele.find(gutui[i].h);
        if(it->second.nluate < it->second.nmax) //putem culege gutuia
        {
            c=1;
            for(it2 = nivele.begin(); it2 !=it; it2++)
               if(it2->second.nluate+1 > it2->second.nmax)
               {
                    c=0;
                    break;
                }
            if(c)
            {
                G += gutui[i].g;
                ntotal--;
                (it->second.nluate)++;
                for(it2 = nivele.begin(); it2 !=it; it2++)
                    (it2->second.nluate)++;
                /*it++;
                for(it2 = it; it2 != nivele.end(); it2++)
                    (it2->second.nmax)--;*/
            }
        }

    }                  

/*    //afisare date citite
    printf("%u %u %u\n",N,H,U);
    for(i=0; i<N; i++)
        printf("%u %u\n",gutui[i].h,gutui[i].g); 
    getch();   


    for(it=nivele.begin(); it!=nivele.end(); it++)
    {
        printf("\n%u %u\n",it->first,it->second.nmax);
    }
    
    getch();
 */  
    fprintf(out,"%u",G);    
    fclose(in);
    fclose(out);    
    return 0;
}