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

typedef struct{
	int inaltime;
	int greutate;
}gutui;

///functie comparare pentru qsort
int compare (const void *a, const void *b){
	gutui *item1 = (gutui*)a;
	gutui *item2 = (gutui*)b;
	
	return -(item1->greutate - item2->greutate);
}

int main(){
	FILE *fin=fopen("gutui.in","r");
	FILE *fout=fopen("gutui.out","w");
	
	int n,h,u;
	int i,j;
	int total=0;
	
	fscanf(fin,"%d %d %d",&n,&h,&u);
	
	gutui *v=(gutui*)malloc(n*sizeof(gutui));
	int *nivel=(int*)malloc(n*sizeof(int));
	
	for (i=0;i<n;i++)
		fscanf(fin,"%d %d",&v[i].inaltime,&v[i].greutate);
		
	qsort(v,n,sizeof(gutui),compare);
	
	///impartirea pe nivele a gutuilor
	for (i=0;i<n;i++)
		if (v[i].inaltime<=h)
			nivel[i]=(h-v[i].inaltime)/u+1;
	
	///descoperirea solutiei (pentru explicatie se consulta readme)
	for (i=0;i<n;i++){
		if (nivel[i]>0 && v[i].inaltime<=h){
			total+=v[i].greutate;
			for (j=i+1;j<n;j++)
				if (nivel[j] >= nivel[i])
					nivel[j]--;
		}
	}
	
	
	fprintf(fout,"%d",total);///solutia finala
	fclose(fin);
	fclose(fout);
	free(v);
	free(nivel);
	return 0;
}