#include <stdio.h>
#include <stdlib.h>
//#include <conio.h>
//using namespace std;
int n,h,u;
typedef struct {
        unsigned int height;
        unsigned int weight;
        unsigned int clas;
        }gutuie;
gutuie *vect;

int my_compare(const void *a,const void *b){
    gutuie *unu=(gutuie *) a;
    gutuie *doi=(gutuie *) b;
    if(unu->clas==doi->clas) return (doi->weight-unu->weight);
    else return (unu->clas-doi->clas);
}
int comp(const void * aa,const void * bb) 
{ int *a=(int *) aa;
  int *b=(int *) bb;
  if (*a==*b)
    return 0;
  else
    if (*a < *b)
        return -1;
     else
      return 1;
}
int main(){
    int i,j,max_dif=0,depl=0,k=0,schimb=0;
    int *solutie;
    FILE *fin=fopen("gutui.in","r");
    FILE *fout=fopen("gutui.out","w");
    fscanf(fin,"%d",&n);
    fgetc(fin);
    fscanf(fin,"%d",&h);
    fgetc(fin);
    fscanf(fin,"%d",&u);
   
    //respect restrictile
    if(n<1||n>10000) 
         return 1;
    vect=(gutuie *)malloc(n*sizeof(gutuie));     
    for(i=0;i<n;i++){
       fgetc(fin);
       fscanf(fin,"%d",&vect[i].height);
       fgetc(fin);
       fscanf(fin,"%d",&vect[i].weight);
       vect[i].clas=(h-vect[i].height)/u+1;
       if(vect[i].clas>max_dif) 
               max_dif=vect[i].clas;
   }
   solutie=(int *)calloc(max_dif,sizeof(int));
   qsort(vect,n,sizeof(gutuie),my_compare);
  /*
  for(i=0;i<n;i++)
      printf("\n%d %d %d ",vect[i].height,vect[i].weight,vect[i].clas);
     */ 
      int g=0;
      i=0;       
      while(i<n){//printf("\ni %d %d %d\n",i,depl,vect[i].clas);
                  k=vect[i].clas;
                  for( g=depl ; g < k && i < n; g++)
                      solutie[depl++]=vect[i++].weight;
                  schimb=0;
                  qsort(solutie,depl,sizeof(int),comp);
                /*  for(g=0;g<depl;g++){
                     printf("%d ",solutie[g]);
                 }   
                 printf("\n%d \n",i);
                 */
              
                 for(g=i;vect[g].clas==k&&schimb<k;g++)
                     for(j=0;j<depl&&schimb<k;j++)
                          if(solutie[j]<vect[g].weight) {
                                 solutie[j]=vect[g].weight;
                                 schimb++;
                                 break; 
                          }
                  i=g;
                  //k++; 
//                  qsort(solutie,depl,sizeof(int),compare1);
                  /*printf("\n");
                  for(g=0;g<depl;g++){
                     printf("%d ",solutie[g]);
                 }   
                 printf("\n");        
                 */
       }
       
                              
          int sum=0;
      for(i=0;i<depl;i++){
          sum+=solutie[i];
  //        printf("%d ",solutie[i]);
          }
          
      fprintf(fout,"%d",sum);
          
//      getch();    
       
    return 0;
}