#include<fstream.h>
ifstream f("lupu.in");
ofstream g("lupu.out");
int n,x,m,l,i,ordonat,aux,d[100001],a[100001];
long long s;
int main()
{
	f>>n>>x>>l;
	for(i=1;i<=n;i++) f>>d[i]>>a[i];
	m=n;
	do{ordonat=1;
	for(i=1;i<=m;i++)
		if(a[i]<a[i+1])
		{aux=a[i];
		a[i]=a[i+1];
		a[i+1]=aux;
		aux=d[i];
		d[i]=d[i+1];
		d[i+1]=aux;
		ordonat=0;}
		m--;} while(!ordonat);
	while(n!=0)
	{if(d[2]+l>x&&d[1]+l<=x)
			{s=s+a[2];
			for(i=2;i<n;i++)
			{a[i]=a[i+1];
			d[i]=d[i+1];}
			n--;}
		else {s=s+a[1];
			for(i=1;i<n;i++)
			{a[i]=a[i+1];
			d[i]=d[i+1];}
			n--;} m=0;
	for(i=1;i<=n;i++) 
	{d[i]=d[i]+l;
	if(d[i]<=x){m++;
	d[m]=d[i];}
	}
	n=m;}
	g<<s;
	f.close(); g.close();
	return 0;
}