#include<fstream>
#define dmax 100003
using namespace std;
ifstream in("lupu.in");
ofstream out("lupu.out");
int n,h[dmax],dim;
long long x,l,t,lana;
struct oaie
{	long long d;
	long long a;
	bool z;
}	oi[dmax];
int father(int k)
{	return k/2;
}
void percolate(int n,int k)
{	long long key=oi[h[k]].a;
	int pi=h[k];
	while(k>1 && key>oi[h[father(k)]].a)
	{	h[k]=h[father(k)];
		k=father(k);
	}
	h[k]=pi;
}
int main()
{	int i,ok,j;
	in>>n>>x>>l;
	for(i=1;i<=n;i++)
	{	in>>oi[i].d>>oi[i].a;
		oi[i].z=1;
	}	
	in.close();
	while(ok)
	{	ok=0;
		for(i=1;i<=n;i++)
		{	if(oi[i].d+(t+1)*l>x && oi[i].z==1)
			{	ok=1;
				dim++;
				h[dim]=i;
				percolate(dim,dim);
				oi[i].z=0;
			}
		}
		if(ok)
			lana+=oi[h[1]].a;
		t++;	
		dim=0;
	}
	out<<lana;
	out.close();
	return 0;
}