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

int n=0;

typedef struct{
	int a;
	int b;
}gut;
			
int compare(const void *x, const void *y){
	return ((gut *)x)->b  - ((gut *)y)->b;
}



int main ()
{
	  int  i,u,h;
	FILE *f1, *f2;
	 
	  gut * gutui;
	f1=fopen("gutui.in","r");
	f2=fopen("gutui.out", "w");
	fscanf(f1,"%d",&n);
	fscanf(f1,"%d",&h);
	fscanf(f1,"%d",&u);
	gutui = ( gut *)malloc( n* sizeof(  gut));

	
	for(i=0;i<n;i++){
		fscanf(f1,"%d",&(gutui[i].a));
		fscanf(f1,"%d", &(gutui[i].b));
		
	}
	
	  int s=0; 
	/*
	for(i=0;i<n;i++)
		printf("%d %d \n",gutui[i].a, gutui[i].b);
		printf("---------------------\n");*/
	qsort( gutui, n, sizeof(gut),compare);
	/*for(i=0;i<n;i++)
		printf("%d %d \n",gutui[i].a, gutui[i].b);*/
	int max=0;
	for(i=0;i<n;i++)
		if((h-gutui[i].a)/u >max ) max= (h-gutui[i].a)/u;
	
	


	//max=k;
	//printf("min%d ", max);
	 int *tmp;
	 tmp= (int*)calloc((max+1), sizeof(int));

		
	for(i=n-1;i>=0;i--){
		if(gutui[i].a<=h){
		if(tmp[(h-gutui[i].a)/u]==0)
			tmp[(h-gutui[i].a)/u]=gutui[i].b; /*printf("%ld ", a[i]);*/
		else
		{
			int  poz =(h-gutui[i].a)/u -1;
			while(poz>=0 && tmp[poz]!=0){
			 poz--;
			}
			
			 if(poz>=0) tmp[poz] =gutui[i].b;
		 }
	 }
		}
	
	for(i=0;i<max+1;i++)
		s=s+tmp[i];
	
	
    fprintf(f2,"%d",s);
    fclose(f1);fclose(f2); 
    return 0;
     
}