#include <stdio.h>
//#include <conio.h>
#include <string.h>
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>


FILE* fs;
FILE* fd;
int N, max_height, height_inc,i,j,x,increase=0,rest,min,k, minmin,kk,kkk,kkkk,maxh,r; 
long long int max_weight=0;

typedef struct {
   int height;
   int weight;
   int getIt;
} gutuie;

gutuie tree[100001];
gutuie newtree[100001];

int compare (const void * a, const void * b)
{
  if(  ( (*(gutuie*)a).height - (*(gutuie*)b).height )  == 0 )
    return ( (*(gutuie*)a).weight - (*(gutuie*)b).weight );
  else return ( (*(gutuie*)a).height - (*(gutuie*)b).height ); 
}

int comp (const void * a, const void * b)
{
  return(*(int*)a - *(int*)b); 
}

using namespace std;

int main(){
    
    fs = fopen("lupu.in","r");
    fd = fopen("lupu.out","w");
    
    if (fs==NULL) {
       printf("Eroare");
       exit (1);
    }
    
    if (fd==NULL) {
       printf("Eroare");
       exit (1);
    }
    
    
    vector<int> coll;
    make_heap (coll.begin(), coll.end());
    
    maxh=0;
    fscanf(fs,"%i",&N);   
    fscanf(fs,"%i",&max_height);
    fscanf(fs,"%i",&height_inc);
    rest = max_height%height_inc;
    max_height=max_height/height_inc;
    for(i=0;i<N;i++){
       fscanf(fs,"%i",&x);
       if(x%height_inc>rest)
          tree[i].height = x / height_inc + 1;
       else
          tree[i].height = x / height_inc;
       fscanf(fs,"%i",&x);
       tree[i].weight = x;
       tree[i].getIt=0;
       if(maxh<tree[i].height &&tree[i].height<=max_height) maxh=tree[i].height;
    }
    
    kk=max_height - maxh;
    
    qsort(tree,N,sizeof(gutuie),compare);
    
    
    kkk=0; kkkk=0;
    for(i=N-1;i>=0;i--){
            if(max_height - tree[i].height == kk){
              
               //printf("salut %i %i %i\n", tree[i].height, tree[i].weight,kk);
               newtree[kkkk]=tree[i];
               kkk++; kkkk++;
               if(kkk>kk) { kk++; kkk=0; }
               }
            else
               if(max_height - tree[i].height > kk){
                 //printf("salut2 %i %i\n", tree[i].height, tree[i].weight);
                 newtree[kkkk]=tree[i];
                 kk=max_height- tree[i].height;
                 kkk=1;
                 kkkk++;
            } 
    }
    
    for(i=0;i<kkkk;i++){
       if((newtree[i].height+increase)<=max_height){
          increase++;
          max_weight = max_weight + newtree[i].weight;
          coll.push_back ((0-newtree[i].weight));
          push_heap (coll.begin(), coll.end());
       }
       else
          if((0-newtree[i].weight) < coll.front()){
          
          max_weight = max_weight + newtree[i].weight;
          max_weight = max_weight + coll.front();
          
          pop_heap(coll.begin(), coll.end());
          coll.pop_back(); 
          coll.push_back ((0-newtree[i].weight));
          push_heap (coll.begin(), coll.end());
          }
    }
    
    fprintf(fd,"%lli",max_weight);
    
    fclose(fs);
    fclose(fd);
    
    
    
}