#include <fstream>
#include <iostream>
#include <queue>
#include <vector>
#define mp make_pair
using namespace std;

priority_queue<pair<int , int > > q;

int main()
{
	int n,X,d,dist,lana;
	ifstream f("lupu.in");
	ofstream g("lupu.out");
	f>>n>>X>>d;
	for(int i=1;i<=n;i++)
	{
		f>>dist>>lana;
		q.push(make_pair(lana,dist));
	}
	
	long long S=0;
	
	for(int i=0;i<=X;i+=d)
	{
		while(q.size() && q.top().second+i>X)
			q.pop();
			
		if(q.size())
			S+=q.top().first;
			q.pop();
	}
	
	g<<S;
	return 0;
}