#include <stdio.h>
#include <stdlib.h>
#include <set>
#include <algorithm>
using namespace std;
const int n_max = 100100;
class set_cmp {
public:
    bool operator() ( const long long  &a, const long long  &b ) { return (a > b); };
};

pair <long long , long long > v[n_max];
multiset <long long, set_cmp> s;

long long i, k, n, x, l, t, p;
long long sol = 0, maxim = 0;
int main()
{
	
	
	freopen("lupu.in","r",stdin);
	freopen("lupu.out","w",stdout);
	scanf("%lld %lld %lld\n", &n, &x, &l);
	for (i = 1; i <= n; ++ i)
	{
		scanf("%lld %lld\n", &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 = v[n].first; i >= 0; --i)
	{
		while ( v[k].first == i && k > 0)
		{
			s.insert(v[k].second);
			--k;
		}
		if (!s.empty())
		{
			sol += *s.begin();
			s.erase(s.begin());
		}
	}
	printf("%lld\n", sol);
	return 0;
}