#include<stdio.h>
#include<stdlib.h>

#define N 100000
typedef struct gutui
{
   int inaltime;
   int greutate;
   int moment;   //momentul la care poate fi culeasa
}gutuie;
int compare(const void *p1,const void *p2)
{
   float aux1,aux2;
   gutuie *g1,*g2;
   g1=(gutuie*)p1; 
   g2=(gutuie*)p2;
   /*aux2=(float)g2->greutate/g2->moment;
   aux1=(float)g1->greutate/g1->moment;
   if(aux2>aux1)
        return 1;
   else
     if(aux2==aux1)
            return g1->moment-g2->moment;
   return -1;*/
   return g2->greutate-g1->greutate;
}  
int maxim(int a,int b)
{
   if(a>b)
     return a;
   return b;
}
int main()
{
  int i,n,h,u;
  int max=0;
  int nr=0,sum=0,aux;
  int culege[N];  //vectorul in care avem 1 daca la momentul i a fost culeasa o gutuie si 0 daca momentul este liber
  FILE *in,*out;
  in=fopen("gutui.in","r");
  out=fopen("gutui.out","w");
  gutuie gut[N];
  fscanf(in,"%d",&n);
  fscanf(in,"%d",&h);
  fscanf(in,"%d",&u);
  for(i=0;i<n;i++){
        fscanf(in,"%d",&gut[i].inaltime);
        fscanf(in,"%d",&gut[i].greutate);
        gut[i].moment=(h-gut[i].inaltime)/u;
  }
  qsort(gut,n,sizeof(gutuie),compare);
  for(i=0;i<n;i++)
      culege[i]=0;
  for(i=0;i<n;i++){
     if(culege[gut[i].moment]==0){
            culege[gut[i].moment]=1;
            max=max+gut[i].greutate;
     }
     else{
         aux=gut[i].moment;
         while(aux>=0 && culege[aux]==1)
                 aux--;
         if(aux>=0){
            max=max+gut[i].greutate;
            culege[aux]=1;
          }
       
     }
 }
  /*for(i=0;i<n;i++)
      if(nr<gut[i].moment){
           max=max+gut[i].greutate;
           nr++;
      }*/
  //printf("%d",max);     
  fprintf(out,"%d",max);
  return 0;
}