#include<cstdio>
#include<algorithm>
using namespace std;
struct oaie
{
	int dist,lana,timp;
};
oaie o[1<<17];
int n,x,l,d,a,j,total;
bool f[1<<30];
bool comp(const oaie &A,const oaie &B)
{
	if(A.lana>B.lana) return true;
	if(A.lana<B.lana) return false;
	if(A.timp<B.timp) return false;
	return true;
}
int cautb(int TIMP)
{
	int i;
	for(i=TIMP;i>=1;i--)
		if(f[i]==false)
			return i;
	return 0;
}
int main()
{
	freopen("lupu.in","r",stdin);
	freopen("lupu.out","w",stdout);
	scanf("%d%d%d",&n,&x,&l);
	for(int i=1;i<=n;i++)
	{
		scanf("%d%d",&d,&a);
		if(d>x)
		{
			--i, --n;
			continue;
		}
		o[i].dist=d;
		o[i].lana=a;
		o[i].timp=(x-d)/l+1;
	}
	sort(o+1,o+n+1,comp);
	for(int i=1;i<=n;i++)
	{
		j=cautb(o[i].timp);
		if(j)
		{
			f[j]=true;
			total+=o[i].lana;
		}
	}
	printf("%d",total);
	return 0;
}