#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
unsigned long suma=0;
void sortare(unsigned long n,unsigned long  *hgutuie,unsigned long  *ggutuie){//sortez descresc dupa h
    unsigned long  aux1,aux2,i,j;
    for (i=0;i<n-1;i++)
        for (j=i+1;j<n;j++)
            if (hgutuie[i]<hgutuie[j]){
                aux1=hgutuie[i];
                hgutuie[i]=hgutuie[j];
                hgutuie[j]=aux1;
                aux2=ggutuie[i];
                ggutuie[i]=ggutuie[j];
                ggutuie[j]=aux2;
            }
}
unsigned long rezolvare(unsigned long  n, unsigned long hmax, unsigned long  u, unsigned long  *maximeh, unsigned long  *maximeg){
    unsigned long  i=0,j=hmax;
    while ((i<n)&&(j>0)){
          if(maximeh[i]<=j){
                           j=j-u;
                           suma+=maximeg[i];
                           }
         // if(maximeh[i]==j){
          //                  suma+=maximeg[i];
          //                  }
          i++;
    }
    return suma;
}
void maxime(unsigned long  n, unsigned long  hmax, unsigned long u, unsigned long *hgutuie, unsigned long *ggutuie, unsigned long *maximeh, unsigned long *maximeg){
     unsigned long i=0,j=hmax;
     for (;i<n,j>0;i++,j=j-u){
         maximeh[i]=hgutuie[i];
         maximeg[i]=ggutuie[i];
     }
}

int main(){
    FILE *fin=fopen("gutui.in","r");
    FILE *fout=fopen("gutui.out", "w");
    unsigned long n,h,u;
    fscanf(fin, "%d %d %d",&n,&h,&u);
    //verific date intrare prima linie corecte
    //printf("numarul de gutui este: %d\ninaltimea maxima este: %d\ninaltime gutuie este: %d\n",n,h,u);
    unsigned long i=0;
    unsigned long *hgutuie=malloc(n*sizeof(unsigned long));//aloc dinamic vect de inalt gutui
    unsigned long *ggutuie=malloc(n*sizeof(unsigned long));//si de greutate gutui
    unsigned long *maximeh=(unsigned long*)calloc(n,n*sizeof(unsigned long));
    unsigned long *maximeg=(unsigned long*)calloc(n,n*sizeof(unsigned long));
    for (i=0;i<n;i++)
        fscanf(fin, "%d %d",&hgutuie[i],&ggutuie[i]);//pun in 2 vectori inaltime si greut coresp gutuie
        //for(i=0;i<n;i++)
        //printf("inaltime:%d, greutate:%d\n",hgutuie[i],ggutuie[i]);//verific vectorii;
        //printf("\n\n\n\n\n");
    sortare(n,ggutuie,hgutuie);
    maxime(n,h,u,hgutuie,ggutuie,maximeh,maximeg);
    sortare(n,maximeh,maximeg);
   //for(i=0;i<n;i++)
     // printf("inaltime:%d, greutate:%d\n",maximeh[i],maximeg[i]);//verific vectorii;
   //printf("%d", rezolvare(n,h,u,maximeh,maximeg));
   //getch();
    //int rasp=rezolvare(n,h,u,maximeh,maximeg);
    fprintf(fout,"%d",rezolvare(n,h,u,maximeh,maximeg));
    fclose(fin);
    fclose(fout);
return 0;
}