#include <iostream>
#include <fstream>
#include <algorithm>
#include <set>
#include <vector>
#define s second
using namespace std;

vector<pair<int,int> > v;
set<int> mp;

int main()
{
	int n,x,l,d,lana;
	ifstream f("lupu.in");
	ofstream g("lupu.out");
	f>>n>>x>>l;
	for(int i=1;i<=n;i++)
	{
		mp.insert(-i);
		f>>d>>lana;
		v.push_back(make_pair(-lana,d));
	}
	sort(v.begin(),v.end());
	int rez=0,maxim=0;
	
	for(unsigned int i=0;i<v.size();i++)
	{
		int tura=(x-v[i].s)/l+1;
		set<int>::iterator it=mp.lower_bound(-tura);
		if(it!=mp.end())
		{
			rez-=v[i].first; 
			mp.erase(it);
		}
	}
	g<<rez;
}