#include<stdio.h>
#include<stdlib.h>
#include<iostream>
typedef struct lol{
        unsigned long greutate;
        unsigned long inaltime;
        }lol;
lol *v;
char ok=0;
unsigned long nr_gutui,inalt_max,pas_inalt;

unsigned long key(unsigned long inaltime){
    return inaltime/pas_inalt;
}

void citire(){
     
     FILE *f=fopen("gutui.in","r");
     fscanf(f,"%lu %lu %lu",&nr_gutui,&inalt_max,&pas_inalt);
     v=(lol*)malloc(sizeof(lol)*nr_gutui);
     for(unsigned i=0;i<nr_gutui;i++)
     {
                  fscanf(f,"%lu %lu",&v[i].inaltime,&v[i].greutate);
                  if(v[i].inaltime>inalt_max)
                               {
                                        i--;
                                        nr_gutui--;
                                        continue;
                               }
                  if(v[i].inaltime%pas_inalt > inalt_max%pas_inalt)
                                             v[i].inaltime=v[i].inaltime/pas_inalt+1;
                  else
                                             v[i].inaltime=v[i].inaltime/pas_inalt;
                  
     }
     v=(lol*)realloc(v,sizeof(lol)*nr_gutui);
    inalt_max/=pas_inalt;          
    fclose(f);
}

void afis(){
     for(int i=0;i<nr_gutui;i++)
     {     
                          printf("%d %d\n",v[i].greutate,v[i].inaltime);
                         
     }
     system("pause");
}

int compare (const void * a, const void * b)
{
  return  -( (*(lol*)a).greutate - (*(lol*)b).greutate );
}


void sortare(){
     qsort (v, nr_gutui, sizeof(lol), compare);
}

int funct(char *vec,unsigned long i, unsigned long ind)
{
    for(;i<inalt_max+1;i++)
            if(vec[i]==0)
            {
                       vec[i]=1;
                       return v[ind].greutate;
            }           
    return 0;
}

int rezolvare2(){
    char *vec=(char*)calloc(inalt_max+1,1);
    if(nr_gutui==0)
                   return 0;
    unsigned long s=0,j;
    for(unsigned long i=0;i<nr_gutui;i++){
                 //j=s;
                 s+=funct(vec, v[i].inaltime,i);
                 //printf("x %d\n",s-j);
    }
    return s;
}
     

                     
int main(){
    FILE *g=fopen("gutui.out","w");
    citire();    
    //afis();
    sortare();
    //afis();
    //printf("%lu\n\n",inalt_max);
    unsigned long s=rezolvare2();
    fprintf(g,"%lu",s);
    //system("pause");
    //printf("\n");
    //afis();
    fclose(g);
    return 0;
}