#include<stdio.h>
#include<algorithm>
using namespace std;
FILE *f=fopen("lupu.in","r");
FILE *g=fopen("lupu.out","w");
long long i,j,n,x,l,d,tmax,a[100001],nr,k,y,maxim,p;
struct oaie{
	  long long lana;
	  long long t;
} oi[100001];
long long total;
int cmp(oaie a, oaie b){
	return(a.t>b.t);
}
void combheap(long long i, long long u){
	  long long s,d;
	  while(2*i<=u)
	  { maxim=a[i];
		  s=2*i;
		  d=2*i+1;
		if(maxim<a[s])
		  { maxim=a[s];
		    p=s;
		  }
		if(maxim<a[d] && d<=u)
		  { maxim=a[d];
		    p=d;
		  }
		if(maxim!=a[i]){
			d=a[i];
			a[i]=maxim;
			a[p]=d;
			i=p;
		}
		else 
			break;
	  }
}
int main(){
nr=0;k=0;
//citim
fscanf(f,"%lld%lld%lld",&n,&x,&l);
for(i=1;i<=n;i++){
	fscanf(f,"%lld%lld",&d,&oi[i].lana);
	if(x-d>=0)
    oi[i].t=1+(x-d)/l;
	else oi[i].t=-1;
	if(oi[i].t>tmax)
		tmax=oi[i].t;
}
//sortam vectorul in functie de timpul maxim la care lupul poate ajunge oaia i
sort(oi+1,oi+n+1,cmp);
i=0;
for(j=tmax;j>=1;j--){ //parcurgem timpii
	while(i<=n&&oi[i+1].t==j) //adaugam toate oile care au timpii egali cu j
    {i++;
	y=oi[i].lana;
	nr++;
	k=nr;
	while(k>1&&y>a[k/2]){  
			a[k]=a[k/2];
			  k=k/2;
		}
		a[k]=y;  //adaugam in heap
    }
if(nr>0){
total+=a[1]; //adaugam maxim-ul la total
a[1]=-1;  //eliminam elementul maxim
combheap(1,nr); //reactualizam heap-ul
if(a[nr-1]==-1)
	a[nr-1]=a[nr];
nr--;
}
}
fprintf(g,"%lld",total);
return 0;
}