#include <stdio.h>
#include <stdlib.h>
#define N 100000 
typedef struct {
	unsigned long int *a;
	unsigned long int n;
	} coada;
int sort(const void *x, const void *y) {
  return (*(int*)x - *(int*)y);
}
void sorta1(unsigned long int a[],unsigned long int n){
qsort(a,n,sizeof(unsigned long int),sort);
}
void sorta2(unsigned long int a[][2],unsigned long int n){
qsort(a,n,sizeof(unsigned long int[2]),sort);
}
void init(coada &q,unsigned long int x){
	q.a=(unsigned long int*)malloc(100000*sizeof(unsigned long int));
	q.n=0;
}
void add(coada &q,unsigned long int x){
	//printf(" %ld \n\n",q.n);
//if(q.n++>100)
	//q.a=(unsigned long int*)realloc(q.a,q.n);
q.a[q.n++]=x;
sorta1(q.a,q.n);
}
void del(coada &q){
for(unsigned long int i=0;i<q.n;i++)
q.a[i]=q.a[i+1];
q.n--;
}
void prin(coada q){
	for(unsigned long int i=0;i<q.n;i++)
		printf(" %ld ",q.a[i]);
	printf("\n");
}
unsigned long int gutui(unsigned long int c[][2],unsigned long int n,unsigned long int h,unsigned long int u){
	unsigned long int i,k=1,m=0;
	coada q;
	init(q,0);
	for(i=0;i<n;i++) 
		 if (c[i][0]>h)	 {
				 c[i][0]=0;
				 c[i][1]=0;}
	for(i=0;i<n;i++) 
		 if (c[i][0]>0)   c[i][0]=h/u-(c[i][0]-1)/u;
	sorta2(c,n);
	//for(i=0;i<n;i++) 	
	//printf("%ld   %ld \n",c[i][0],c[i][1]);
	for(i=0;i<n;i++)
		if(k<=c[i][0])  { 
				m=m+c[i][1];
				add(q,c[i][1]);
				//prin(q);
				k++;
				}
			else  if (c[i][1]>q.a[0]) 
					 { m=m-q.a[0]; 
					   m=m+c[i][1];
						del(q);
					   add(q,c[i][1]);
						//prin(q);
					}
return m;
}
int main(){
	 unsigned long int c[100000][2];
	 unsigned long int i,n,h,gr,j,u;
         freopen("gutui.in", "r", stdin);
         freopen("gutui.out", "w", stdout); 
         scanf("%ld",&n);
	 scanf("%ld",&h);
	 scanf("%ld",&u);
 	 for (i=0;i<n;i++) { 
     	 		scanf("%ld",&c[i][0]);
			scanf("%ld",&c[i][1]);
			c[i][2]=0;
	}
	gr=gutui(c,n,h,u);
	printf("%ld\n",gr);
	return 0;
}