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

struct oaie{
	int a,t;
}o[100000];

int main()
{
	vector <int> h;
	int smax=0,n,x,l,i,d,tmax=0,j,k=0,z;
	FILE *f=fopen("lupu.in","r");
	FILE *g=fopen("lupu.out","w");
	fscanf(f,"%d %d %d",&n,&x,&l);
	if(l==0)
		for(i=0; i<n;i++) {
			fscanf(f,"%d %d",&d,&z);
			smax+=z;
		}
	else {
		for(i=0; i<n; i++) {
			fscanf(f,"%d %d",&d,&o[i].a);
			o[i].t=(x-d)/l+1;
			if(o[i].t>tmax) tmax=o[i].t;
		}
		//for(i=0; i<n; i++) printf("%d\n",o[i].t);
		//printf("%d\n",tmax);
		for(i=tmax; i>=1; i--) {
			k=0;
			for(j=0; j<n;j++)
				if(o[j].t==i) {
					h.push_back(o[j].a);
					k++;
				}
			/*printf("%d:\n",i);
			for(z=0; z<k; z++) printf("%d ",h[z]);*/
			make_heap(h.begin(),h.end());
			smax+=h.front();
			while(k) {
				h.pop_back();
				k--;
			}
			//printf("\n");
		}
	}
	fprintf(g,"%d",smax);
	fclose(f);
	fclose(g);
	return 0;
}