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


typedef struct{
	int h;
	int g;
}gutuie;


int compare(const void *a,const void *b){
	gutuie * first=(gutuie *) a;
	gutuie * second=(gutuie *) b;
	return (second->g - first->g);
}
int main(){
gutuie sir[100000];
int i;
FILE *fp=fopen("gutui.in","r");
FILE *fp1=fopen("gutui.out","w");
char s[80];
fgets(s,80,fp);

char *sep=" ";
int N=atoi(strtok (s,sep));

int H=atoi(strtok (0,sep));

int U=atoi(strtok (0,sep));

int n=0;

int a[N];
while ( fgets(s,80,fp) != NULL ){
	sir[n].h=atoi(strtok (s,sep));
	sir[n].g=atoi(strtok (0,sep));
	a[n]=0;
	n++;
}//end while

fclose (fp);
int g=0;
qsort(sir,N,sizeof(gutuie),compare);




for( i=0; i<N;i++){
	
	n=(H-sir[i].h)/U+1;
	 
	while ((a[n]!=0) && (n>0))
		n--;
	
	if (n>0) 
		a[n]=sir[i].g;
			
}

for (i=1; i<=H/U+1; i++){
	
	if (a[i]!=0)
		g=g+a[i];
	else break;
}

	

fprintf(fp1,"%d",g);
fclose(fp1);
}