#include<fstream>
#include<set>
#include<algorithm>
using namespace std;
ifstream in("lupu.in");
ofstream out("lupu.out");

struct oaie{
	int sup, lan;
};

const int nmax = 100006;
int n, x, l, ce;
oaie v[nmax];
multiset <int> s;
long long rasp;

int compar(oaie a, oaie b)
{
	return a.sup<b.sup;
}

int main(){
	int player_unu=0;

	in>>n>>x>>l;
	for(int i = 1; i<=n; i++)
	{
		in>>v[i].sup>>v[i].lan;

		if(v[i].sup>x)
		{
			n--;
			i--;
		}
		else
		{
			v[i].sup = (x - v[i].sup) / l + 1;
		}
	}

	sort(v + 1, v + n + 1, compar);

	s.insert(-v[n].lan);
	for(int i = n - 1; i>=0; i--)
	{
		if(v[i].sup!=v[i + 1].sup)
		{
			ce = v[i + 1].sup - v[i].sup;

			while(s.empty()==0 && ce!=0)
			{
				ce--;
				rasp += (long long)(-(*s.begin()));
				s.erase(s.begin());
			}

			s.clear();
		}

		s.insert(-v[i].lan);
	}

	out<<rasp<<'\n';

	return player_unu;
}