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

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

int compara(void* a,void* b)
{
    unsigned int val_a,val_b,vala,valb;
    val_a=(*((gutuie *)a)).h;
    val_b=(*((gutuie *)b)).h;
    vala=(*((gutuie *)a)).g;
    valb=(*((gutuie *)b)).g;
    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("gutui2.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);
     unsigned int *ridicari,*nivele;
    gutuie *date;
    date=(gutuie*) calloc(N,sizeof(gutuie));

    int i,m=0;
    unsigned int nr_max_gutui;
   // ridicari = (unsigned int *) calloc(N,sizeof (unsigned int));
     nivele = (unsigned int *) calloc(N+2,sizeof (unsigned int));


    //citim datele despre fiecare creanga
    for(i=0;i<N;i++)
        fscanf(in,"%u%u",&date[i].h,&date[i].g);

    qsort(date,N,sizeof(gutuie),(__compar_fn_t)&compara);
   for(i=1;i<=N+1;i++)
        nivele[i]=0;
 // 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
    
   // printf ("%d \n", nr_max_gutui);
    int culese=0;
    long int suma=0;
    
    nivele[0]=-1;
    for(i=0;i<N;i++) 
     {  
        m=(H-date[i].h)/U+1;
       if (m>0)
         if (culese<nr_max_gutui)

            if(nivele[m]<m){
   //poate fi culeasa in conditiile date
		 if (nivele[m]==(m-1))
			{      //printf ("%d\n",m);
				if (nivele[m-1]!=(m-1) &&nivele[m+1]!=m)
            			{   
                			 suma+=date[i].g;
               				 culese++;
                			 nivele[m]++;}else ;}
                else
			{
				suma+=date[i].g;
               			 culese++;
                		nivele[m]++;}
            }}

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

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