#include <stdio.h>
#include <stdlib.h>
#include <set>
#include <algorithm>
using namespace std;
const int n_max = 100100;
pair <long long , long long > v[n_max];
set <long long > s;
set <long long >::iterator it2;
int main()
{
	long long i, k, n, x, l, t, p;
	long long sol = 0, maxim = 0;
	freopen("lupu.in","r",stdin);
	freopen("lupu.out","w",stdout);
	scanf("%lld %lld %lld", &n, &x, &l);
	for (i = 1; i <= n; ++ i)
	{
		scanf("%lld %lld", &t, &v[i].second);
		v[i].first = (x-t)/l;
		if (v[i].first > maxim) maxim = v[i].first;
	}
	sort(v+1, v+n+1);
	k = n;
	for (i = maxim; i >= 0; --i)
	{
		while ( v[k].first == i && k > 0)
		{
			s.insert(v[k].second);
			--k;
		}
		if (!s.empty())
		{
			it2 = s.end();
			--it2;
			p = *it2;
			s.erase(p);
			sol = (long long) sol + p;
		}
	}
	printf("%lld\n",sol);
	return 0;
}