#include<fstream>
#include<algorithm>
using namespace std;
ifstream in("lupu.in");
ofstream out("lupu.out");
struct oi{
	int dist,lana;
}v[100001];
bool cmp( oi a,oi b)
{
	return a.dist>b.dist;
}
int n,x,l,s;
int main()
{
	int i=1,j=1,k,l,p,q,max;
	in>>n>>x>>l;
	for(i=1;i<=n;i++)
	{
		in>>v[i].dist>>v[i].lana;
		if(v[i].dist>x)
			i--;
	}
	sort(v+1,v+n+1,cmp);
//	for(i=1;i<=n;i++)
		//out<<v[i].dist<<" "<<v[i].lana<<"\n";
//	out<<"\n";
	
	while(v[n].dist<=x)
	{
		max=-1;
		j=1;		
		while(v[i].dist>x)i++;
		while(v[j].dist+l>x)
		{
			if(v[j].lana>max)
			{
				max=v[j].lana;
				p=i;
			}
			j++;
		}
		s+=max;
		if(p==n)
			break;
		for(i=1;i<=n;i++)
			v[i].dist+=l;
	}
	out<<s;
	return 0;
}