#include <iostream>
#include <fstream>
#include <set>
#include <vector>
#include <algorithm>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");

//x->distanta max la care lupul poate alege oi
//l->distanta cu care se muta toate oile dupa fiecare alegere
int n, x, l;
vector<pair<int,int>> v;
multiset <int> s;
void citire()
{
	f >> n >> x >> l;
	int i;
	v.resize(n + 3);
	for (i = 0; i <n; i++)
	{
		f >> v[i].first >> v[i].second;
	}
	f.close();
}
int main()
{
	citire();
	sort(v.begin(), v.begin() + n);
	int i;
	/*for (i = 0; i <= n; i++)
		g << v[i].first << " ";*/
	int q = x % l;
	for (i = 1; i <= q; i++)
	{
		s.insert(-v[i].second);
	}
	int suma = 0;
	if (q)
	{
		suma += (*s.begin());
		s.erase((*s.begin()));
		q++;
	}
	for (i = q; i <= x; i++)
	{
		s.insert(-v[i].second);
		if (i%l == 0)
		{
			suma += (*s.begin());
			s.erase((*s.begin()));
		}
	}
	g << -suma << "\n";
	g.close();
	return 0;
}