#include<stdio.h>
#include<algorithm>
using namespace std;
FILE*f=fopen("lupu.in","r");
FILE*g=fopen("lupu.out","w");
int nr,n,x,l;
long long sol;
struct oi
{
	int d,a;
}v[100001];
int cmp(oi a,oi b)
{
	return a.d<b.d;
}
int d[100001];
char viz[100001];
void insert(int x)
{
	d[++nr]=x;

	int k=nr;
	while(k>1&&d[k/2]<d[k])
	{
		d[0]=d[k];
		d[k]=d[k/2];
		d[k/2]=d[0];
		k/=2;
	}
}
void down(int x,int k)
{
	d[k]=d[nr--];
	int son;
	do
	{
		son=0;
		if(2*k<=nr)
			son=2*k;
		if(2*k+1<=nr&&d[son]<d[2*k+1])
			son++;
		if(d[son]>d[k])
		{
			d[0]=d[k];
			d[k]=d[son];
			d[son]=d[0];
			k=son;
		}
		else
			son=0;
		
	}while(son);

}
int main()
{
	fscanf(f,"%d%d%d",&n,&x,&l);
	for(int i=1;i<=n;++i)
		fscanf(f,"%d%d",&v[i].d,&v[i].a);
	
	sort(v+1,v+n+1,cmp);
	int max=0;
	int ok;
	for(int i=1;i<=n;++i)
	{
		ok=0;
		if(v[i].d<=x)
			ok=1;
		v[i].d=(x-v[i].d)/l;
		if(ok)
			++v[i].d;
		if(v[i].d>max)
			max=v[i].d;
	}
	int j=1;
	for(int i=max;i&&j<=n;--i)
	{
		while(v[j].d==i)
		{
			insert(v[j].a);
			++j;
		}
		if(nr)
		{
			sol+=d[1];
			down(v[j].a,1);
		}
		
	}
	
	fprintf(g,"%lld",sol);
	
	fclose(f);
	fclose(g);
	return 0;
}