#include <stdio.h>

long int dist[100000],lana[100000],T[100000];
long int N,X,L;

long int poz(long int li,long int ls){
   long int c,i=1,j=0;
   while(li<ls){
     if(lana[li]<lana[ls]){
	  c=dist[li];
	  dist[li]=dist[ls];
	  dist[ls]=c;
	 
	  c=lana[li];
	  lana[li]=lana[ls];
	  lana[ls]=c;

	  c=i;
	  i=-j;
	  j=-c;
       }
   li+=i;
   ls+=j;
   }
   return li;
}

void sortare(long int li, long int ls){
   long int k;
   if(li<ls){
     k=poz(li,ls);
     sortare(li,k-1);
     sortare(k+1,ls);
   }
}

long int transa(long int d){
   long int dif=X-d;
   return dif/L;
}


void bubble(long int li, long int ls){
   long int c,ok=0;
   long int i;
   while(!ok){
      ok=1;
      for(i=li;i<ls;i++){
         if(T[li]>T[ls]){
              c=dist[li];
           	  dist[li]=dist[ls];
	            dist[ls]=c;
	  
	            c=lana[li];
	            lana[li]=lana[ls];
	            lana[ls]=c;

	            c=T[li];
	            T[li]=T[ls];
	            T[ls]=c;
	            ok=0;

         }
      }
   }
}


int main(){
 
  long int i;
  long int k=0;
  FILE *fin=fopen("lupu.in","r");
  fscanf(fin,"%ld%ld%ld",&N,&X,&L);
  for(i=0;i<N;i++){
    fscanf(fin,"%ld%ld",&dist[k],&lana[k]);
    if(dist[k]<=X)k++;
    //indice[i]=i+1;
  }
  N=k;
  //sortez decrescator dupa lana
  sortare(0,N-1);
  //sortez crescator dupa timp, ... asociez fiecarei distante un ti (transa din care face parte)
  long int li=0,ls=0;
  while(ls<N){
     T[ls]=transa(dist[ls]);
     if(lana[li]!=lana[ls]){
       bubble(li,ls-1);//sortez crescator dupa T, pe intervalul [li,ls)
       //printf("sortez in intervalul [%d,%d)\n",li,ls);
       li=ls;
     }
     ls++;
  }  
  //o afisare
 
/*   for(i=0;i<N;i++){
     printf("%2d ",i+1);
  }
  printf("\n");
   
  for(i=0;i<N;i++){
     printf("%2d ",lana[i]);
  }
  printf("\n");

  for(i=0;i<N;i++){
     printf("%2d ",T[i]);
  }
  printf("\n");
  */
  //parcurg vectorul...
   long int nr_oii=0;
   long long int g=0;
   for(i=0;i<N;i++){
    
     if(T[i]>=nr_oii){//nu am mai ales o oaie din
        //viz[T[i]]=1;
        nr_oii++;
    //    printf("aleg oaia");
     //   printf("%d\n",i+1);
        g+=lana[i];
     }
   }
   FILE *fout=fopen("lupu.out","w");
   fprintf(fout,"%ld\n",g);
    
}