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

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

/*int compare (const void *a, const void *b){
	const gutui *item1=a,*item2=b;
	if (item1->inaltime <item2->inaltime)
		return 1;
	else if (item1->inaltime > item2->inaltime)
		return -1;
	else
		return 0;
}*/

int compare (const void *a, const void *b){
	gutui *item1 = (gutui*)a;
	gutui *item2 = (gutui*)b;
	
	//printf("ggggg %d\n",item1->inaltime);
	
	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,temp,j,srs;
	int total=0;
	
	fscanf(fin,"%d %d %d",&n,&h,&u);
	
	gutui *v=(gutui*)malloc(n*sizeof(gutui));
	//int *x=(int*)malloc(n*sizeof(int));
	int *serie=(int*)malloc((h+3)*sizeof(int));
	int *nivel=(int*)malloc(n*sizeof(int));
	
	srs=1;
	temp=0;
	for (i=h;i>0;i--){
		serie[i]=srs;
		temp++;
		if (temp==u){
			temp=0;
			srs++;
		}
	}
	
	
	
	for (i=0;i<n;i++)
		fscanf(fin,"%d %d",&v[i].inaltime,&v[i].greutate);
		
	/*for (i=0;i<n;i++)
		printf("%d %d\n",serie[v[i].inaltime],v[i].greutate);
		
	printf("\n");*/
	

		
	qsort(v,n,sizeof(gutui),compare);
	
	for (i=0;i<n;i++)
		nivel[i]=serie[v[i].inaltime];
	
	/*for (i=0;i<n;i++)
		printf("%d\t%d\n",v[i].inaltime,v[i].greutate);*/
	
	for (i=0;i<n;i++){
		if (v[i].inaltime <= h)
		if (nivel[i]>0){
			//printf("%d \n",v[i].greutate);
			total+=v[i].greutate;
			for (j=i+1;j<n;j++)
				if (nivel[j] >= nivel[i])
					nivel[j]--;
		}
	}
	
	
	fprintf(fout,"%d",total);
	fclose(fin);
	fclose(fout);
	free(v);
	//free(x);
	free(serie);
	free(nivel);
	return 0;
}