#include<stdio.h>
#include<stdlib.h>
typedef struct fruct{
	unsigned int ht;
	unsigned int wt;
	unsigned int niv;
} fruct;
int compare ( const void * a, const void * b){
	fruct f1, f2;
	f1 = *(fruct*)a;
	f2 = *(fruct*)b;
	return f2.wt-f1.wt;
}
/*int search (int v[], int start,int end){
	int mij= (start+end)/2;
	if ( v[mij]==0 )
		return mij;
	
	
}*/
int main (){
	FILE * fin = fopen ( "gutui.in", "r");
	FILE * fout = fopen ( "gutui.out", "w");
	long n, u, h;
	int i;
	fruct vec[100002];
	fscanf( fin, "%ld", &n);
	fscanf( fin, "%ld", &h);
	fscanf( fin, "%ld", &u);
	int min=0;
	for ( i=0; i<n; i++ ){
		fscanf (fin, "%d%d", &vec[i].ht, &vec[i].wt);
		vec[i].niv=(h-vec[i].ht)/u+1;
		if (vec[i].niv<min)
			min = vec[i].niv;
	}
	i=0;
	unsigned int prada = 0;
	int j;
	qsort(vec, n, sizeof(fruct), compare);
	int m;
	m = h/u;
	//printf("%d\n",m);
	int level[m+2];
	for (i=1; i<m+1; i++)
		level[i] = -1;
	for (i=0; i<n; i++){
		if (vec[i].ht<h){
			if ( level[vec[i].niv]==-1 )
				level[vec[i].niv]=i;
			else{
				for (j=1; j<vec[i].niv; j++)
					if ( level[j]==-1 )
						break;
				//printf("**%d\n", j);
				if (j<vec[i].niv)
					level[j]=i;
			}
		}
	}
	for (i=1; i<m+1; i++)
		if (level[i]!=-1){
			//printf("%d ", vec[level[i]].wt);
			prada = prada + vec[level[i]].wt;
		}
	//printf("\n");
	//printf("%d\n",prada);		
	/*for (i=0; i<n; i++)
		printf("%d %d %d\n",vec[i].ht, vec[i].wt, vec[i].niv);*/
	fprintf (fout,"%d\n", prada);
	fclose ( fin );
	fclose ( fout );
	return 0;
}