#include <stdio.h>
#include <stdlib.h>


typedef struct  
{
	long g;
	long h;
	long nr;
}nivel;

int cmp(const void* a, const void* b)
{
	static long rez;
	rez=((nivel*)b)->g-((nivel*)a)->g;
//	if(rez==0) rez=((nivel*)a)->h-((nivel*)b)->h;
	return rez;
}


int main()
{
	FILE *fin=fopen("gutui.in", "r");
	FILE *fout=fopen("gutui.out", "w");

	int n, i;
	long h, u, nivmax, nniv=0, max=0, j;
	nivel *v;
	long *rez;

	fscanf(fin, "%d%ld%ld", &n, &h, &u);
	nivmax=h/u+1;

	v=(nivel*)calloc(n, sizeof(nivel));
	rez=(long*)calloc(nivmax, sizeof(long));

	for(i=0;i<n;++i)
	{
		fscanf(fin, "%ld%ld", &v[i].h, &v[i].g);
		v[i].nr=(h-v[i].h)/u;
		if(v[i].h==0) v[i].nr=nivmax-1;
//		if( (v[i].h>h) || (v[i].g<1) ) {--i; --n;}
	}

	qsort(v,n,sizeof(nivel),cmp);
	
	i=0;
	while( (nniv<nivmax) && (i<n) )
	{
		j=v[i].nr;
		while(j>-1)
		{
			if(rez[j]==0) { max+=rez[j]=v[i].g; ++nniv; break; }
			--j;
		}
		++i;
	};
	
	fprintf(fout, "%ld", max);

	free(v);
	free(rez);

	fclose(fin);
	fclose(fout);
	return 0;
}