#include <stdio.h>
#include <stdlib.h>
#include <set>
#include <algorithm>
using namespace std;
const int n_max = 100001;
pair <int , int > v[n_max];
set <int > s;
set <int >::iterator it2;
int main()
{
	int i, k, n, x, l, t, sol = 0, p;
	freopen("lupu.in","r",stdin);
	freopen("lupu.out","w",stdout);
	scanf("%d %d %d", &n, &x, &l);
	for (i = 0; i < n; ++ i)
	{
		scanf("%d %d", &t, &v[i].second);
		v[i].first = (x-t)/l;
	}
	sort(v, v+n);
	k = n-1;
	for (i = v[n-1].first; i >= 0; --i)
	{
		while ( v[k].first == i && k >= 0)
		{
			s.insert(v[k].second);
			--k;
		}
		it2 = s.end();
		--it2;
		p = *it2;
		s.erase(p);
		sol +=p;
	}
	printf("%d\n",sol);
	return 0;
}