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

int main()                 //n nr gutui, h inaltimea maxima, u inaltime ridicare
{    FILE *f, *g;
     int n,h,u;
   int hg[100000] ,wg[100000] ,v[100000];
    int min=h;
    int i;
    int j;
    int maxh,maxw;
    int x=h;
    int contor=0;
    int greutate=0;
    f=fopen("gutui.in","r");
    g=fopen("gutui.out","w");
    fscanf(f,"%d",&n);
    fscanf(f,"%d",&h);
    fscanf(f,"%d",&u);
    for(i=0;i<n;i++)
     {fscanf(f,"%d",&hg[i]);
      fscanf(f,"%d",&wg[i]);
      v[i]=0;
       if(hg[i]<min) min=hg[i];}
    for(i=0;i<=(h-min)/u;i++)
      {maxh=min;
      maxw=0;
      for(j=0;j<n;j++)
        {if(hg[j]<=x)
          {if((hg[j]-maxh>=u)&&(v[j]!=1)) {maxh=hg[j];
                                          maxw=wg[j];
                                          contor=j;}
           else
             if((abs(hg[j]-maxh)<u)&&(wg[j]>maxw)&&(v[j]!=1)) {maxh=hg[j];
                                                               maxw=wg[j];
                                                               contor=j;}
          }
         }

          v[contor]=1;
          greutate=greutate+maxw;
          x=x-u;
       }
         fprintf(g,"%d",greutate);
       fclose(f);
      fclose(g);
      return 0;
}