#include <stdio.h>
#define maxl 100010
int sum=0,t,i,j,k,n,x,l;
int d[maxl],a[maxl],b[maxl][2];
int heap[maxl];
void inter(int p, int q)
{
	 int r=(p+q)/2,i,x=p,y=r+1;
	 k=0;
	 while (x<=r && y<=q)
	 {
		k++;
		if (d[x]<d[y]) {b[k][0]=d[x];b[k][1]=a[x];x++;}
		else {b[k][0]=d[y];b[k][1]=a[y];y++;}
	 }
	 while (x<=r) {k++;b[k][0]=d[x];b[k][1]=a[x];x++;}
	 while (y<=q) {k++;b[k][0]=d[y];b[k][1]=a[y];y++;}
	 k=0;
	 for (i=p; i<=q; i++) {k++;d[i]=b[k][0];a[i]=b[k][1];}
}
void inter2(int p, int q)
{
	 int r=(p+q)/2,i,x=p,y=r+1;
     k=0;
	 while (x<=r && y<=q)
	 {
		k++;
		if (a[x]<a[y]) {b[k][0]=d[x];b[k][1]=a[x];x++;}
		else {b[k][0]=d[y];b[k][1]=a[y];y++;}
	 }
	 while (x<=r) {k++;b[k][0]=d[x];b[k][1]=a[x];x++;}
	 while (y<=q) {k++;b[k][0]=d[y];b[k][1]=a[y];y++;}
	 k=0;
	 for (i=p; i<=q; i++) {k++;d[i]=b[k][0];a[i]=b[k][1];}
}
void merge(int p, int q)
{
	int r=(p+q)/2;
	if (p==q) return;
	merge(p,r);
	merge(r+1,q);
	inter(p,q);
	if (p>=q) return;
}
int main()
{
	freopen("lupu.in","r",stdin);
    freopen("lupu.out","w",stdout);
    
    scanf("%d %d %d",&n,&x,&l);    
    for (i=1; i<=n; i++)
        scanf("%d %d",&d[i],&a[i]);
    
	for (i=1; i<=n; i++) 
     if (d[i]>x) d[i]=-1;     
     else d[i]=(x-d[i])/l;

	merge(1,n);

	k=0;
	int timp=-1;
	for (i=n; i>=1; i--)
	if (d[i]!=timp && d[i]>=0)
	{
		 for (j=i; j>=1; j--)
		 if (d[j]==d[i])
		 {
			k++;
			heap[k]=a[j];
			x=k;
			while (x/2>0)
			{
				if (heap[x/2]<heap[x])
				{
					t=heap[x/2];
					heap[x/2]=heap[x];
					heap[x]=t;
				}
				x/=2;
			}
		}
		else break;
		sum+=heap[1];

		// eliminare pozitia 1 din heap
		t=heap[1];heap[1]=heap[k];heap[k]=t;k--;
		x=1;
		while (x*2<=k)
		{
			int p=2*x,q=2*x;
			if (2*x+1<=k) q++;
			if (heap[p]>heap[q])
			{
				t=heap[x];
				heap[x]=heap[p];
				heap[p]=t;
				x=p;
			}
			else
			{
				t=heap[x];
				heap[x]=heap[q];
				heap[q]=t;
				x=q;
			}
		}

		timp=d[i];
	}
	printf("%d\n",sum);
    return 0;
}