#include <iostream.h>
#include <stdio.h>
#include <algorithm>
#define nmax 100001
using namespace std;

struct oi  {int d,a,t;}   oaie[nmax],z;
int n,nroi,x,l,S,h[nmax],i,j;

void urca(int nod)
      {int aux;
       while(nod/2 && h[nod/2]<h[nod])     
                   {aux=h[nod/2];h[nod/2]=h[nod];h[nod]=aux;
                    nod/=2;}
      }
void coboara(int nod)
     {int nodfiu=0,aux; 
      while(nodfiu!=nod)
              {nodfiu=nod;
               if(nodfiu*2<=h[0] && h[nod]<h[nodfiu*2])      nod=nodfiu*2;
               if(nodfiu*2+1<=h[0] && h[nod]<h[nodfiu*2+1])  nod=nodfiu*2+1;
               aux=h[nodfiu];h[nodfiu]=h[nod];h[nod]=aux;
               }
      }
void citire() 
     {freopen("lupu.in","r",stdin);
      scanf("%d %d %d",&n,&x,&l);
      for(i=1;i<=n;i++)   scanf("%d %d",&oaie[i].d,&oaie[i].a);
      fclose(stdin);
      }
void scriere()
     {freopen("lupu.out","w",stdout);
      printf("%d\n",S);
      fclose(stdout);
      }
bool cmp(oi u1,oi u2)
     {return u1.t<u2.t;}
int main()
    {citire();
     if(!l)     {for(i=1;i<=nroi;i++)     
                           S+=oaie[i].a;  
               }
     else      {for(i=1;i<=n;i++)       
                        oaie[i].t=1+(x-oaie[i].d)/l;
                sort(oaie+1,oaie+1+n,cmp);
                j=n;
                for(i=oaie[nroi].t;i>=1;i--)
                           {for(;j>=1;j--)
                                     {if(oaie[j].t==i)         
                                                  {h[++h[0]]=oaie[j].a;urca(h[0]);}
                                      else                 
                                                   break;
                                      }
                            if(h[0])
                                {S+=h[1];h[1]=h[h[0]--];
                                coboara(1);}
                            }
                }
     scriere();
     return 0;
     }