#include <fstream>
#include <vector>
#include <algorithm>
#include <queue>

using namespace std;

bool comp (pair<int, int> x, pair<int, int> y)
{	
	return x.first>y.first;
}

int main()
{
	ifstream in ("lupu.in");
	ofstream out ("lupu.out");

	int  n, x, l, D, L, i, tm=0;
	int cl = 0;
	vector<pair<int, int> > oi;
	priority_queue <int> que;

	in>>n>>x>>l;

	for (i=0; i<n; i++)
	{
		in>>D>>L;
		if(D <= x)
		{
			oi.push_back(make_pair((x-D)/l, L));
			if ((x-D)/l > tm)
				tm = (x-D)/l;
		}
	}

	sort(oi.begin(), oi.end(), comp);

	int j=0;
	for(i=tm; i>=0; i--)
	{
		while(oi[j].first == i && j<oi.size())
			que.push(oi[j++].second);
		
		if(!que.empty())
		{
			cl+=que.top();
			que.pop();
		}
	}

	out<<cl;

	return 0;
}