#include <cstdio>
#include <algorithm>
using namespace std;

struct nod
{long long  d,l;} v[100002];

int cmp(const nod &x,const nod &y)
{
	if (x.d!=y.d) return x.d<=y.d; else
		return x.l>=y.l;
}

int main()
{
	int n,i,nr=0;
	long long x,l,d=0,sol=0;
	
	freopen("lupu.in","r",stdin);
	freopen("lupu.out","w",stdout);
	scanf("%d %lld %lld",&n,&x,&l);
	for (i=1;i<=n;++i)
	{
		scanf("%lld %lld",&v[nr+1].d,&v[nr+1].l);
		if (v[nr+1].d<=x) ++nr,v[nr].d=(x-v[nr].d)/l;
	}
	sort(v+1,v+nr+1,cmp);
	for (i=1;i<=nr;++i)
	{
		if (v[i].d>=d) 
			sol+=v[i].l,++d;
	}
	printf("%lld",sol);
	return 0;
}