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

typedef struct{
    unsigned int h; //inaltimea crengii pe care se afla gutuia
    unsigned int g; //greutatea gutuii
    unsigned int level;
} gutuie;

int compara(void* a,void* b)
{
    unsigned int val_a,val_b,vala,valb;
    val_a=(*((gutuie *)a)).g;
    val_b=(*((gutuie *)b)).g;
    vala=(*((gutuie *)a)).level;
    valb=(*((gutuie *)b)).level;
    if(vala<valb)
        return 1;
    else
        if(vala>valb)
            return -1;
        else
        {
            if(val_a<val_b)
                return 1;
            else
                if(val_a>val_b)
                    return -1;
                else
                    return 0;
        }
}

int main()
{
    //deschidere fisier de intrare, respectiv fisier de iesire
    FILE *in,*out;
    in=fopen("gutui.in","r");
    out=fopen("gutui.out","w");

    //citim numarul de gutui, inaltimea maxima si cu cat se ridica crengile
    int N,H,U;
    fscanf(in,"%d%d%d",&N,&H,&U);
     
    gutuie *date,*sol;
    date=(gutuie*) calloc(N,sizeof(gutuie));
    sol=(gutuie*) calloc(N,sizeof(gutuie));
    int i,*vmin;
    unsigned int nr_max_gutui;

     vmin=(int*)calloc (N,sizeof(int));


    for(i=0;i<N;i++)
        fscanf(in,"%u%u",&date[i].h,&date[i].g);

    for (i=0;i<N;i++)
		date[i].level=(H-date[i].h)/U+1;
    
    qsort(date,N,sizeof(gutuie),(__compar_fn_t)&compara);
   
 // for(i=0;i<N;i++)
     //  printf("%u %u\n",date[i].h,date[i].g);
    unsigned int minim=date[0].h;

    for(i=1;i<N;i++)

        if(date[i].h<minim)
            minim=date[i].h;

    //printf("%u\n",minim);
    
    nr_max_gutui=(H-minim)/U + 1;  //cate gutui ar putea fi maxim culese a.i. sa se respecte conditiile
   
    

	
 
         
  
    int culese=0;
    long int suma=0;
    int j,min,k;
    
    
	for (i=0;i<N;i++)
		{ if (culese<nr_max_gutui && date[i].level>culese)
			{sol[i]=date[i]; culese++;
				if(min>sol[i].g) {min=sol[i].g; k=i;vmin[j++]=min;}}
                  else
			{if (date[i].g>min) sol[k]=date[i];}
				
			}
			
    for (i=0;i<nr_max_gutui;i++)
		suma=suma+ date[i].g;

        fprintf(out,"%ld\n",suma);

    free(date);
    fclose(in);
    fclose(out);
    return 0;
}