#include <stdio.h>
using namespace std;
int elem=0, heap[100000];
void addheap(int lana);
int main() {
    int n, x, l, lung[100000], lana[100000], suma=0, i, j, pas, t;
    FILE *in = fopen("lupu.in", "r"), *out = fopen("lupu.out", "w");
    fscanf(in, "%d%d%d", &n, &x, &l);
    for(i=1; i<=n; i++) {
             fscanf(in, "%d%d", &lung[i], &lana[i]);
    }
    pas=n; t=1;
    while(pas>0) {
             for(i=1; i<=n; i++) {
                          if(lung[i]+t*l>x) {
                               pas--; addheap(lana[i]);
                               lung[i]=-1000;
                      }
             } t++;
             suma+=heap[1]; elem=0;
    }
    fprintf(out, "%d", suma);
    fclose(in); fclose(out);
    return 0;         
}

void addheap(int lana) {
     int s, k;
     elem++;
     heap[elem]=lana;
     s=elem;
     if(s==1) { return; }
     while(s>1 && heap[s]>heap[(int)s>>1]) {
          k=heap[s];
          heap[s]=heap[(int)s>>1];
          heap[(int)s>>1]=k;
          s=(int)s>>1;
     }
}