#include<stdio.h>
#define min(i, x) (((i) < (x))?(i):(x))

int i, j, N, H, U, tN;
int h[100000], g[100000], t[100000];

void swap(int i, int j){
     int aux = h[i];
     h[i] = h[j];
     h[j] = aux;
     aux = g[i];
     g[i] = g[j];
     g[j] = aux;
}

int partitie(int left, int right){
    int i, j, x = h[left];
    i = left;
    for(j = left + 1; j <= right; j++)
       if(h[j] > x){
               i = i + 1;
               swap(i, j);
       }        
    swap(left, i);
    return i;
}

void qsort(int left, int right){
     if(left >= right)
       return;
     int poz = partitie(left, right);
     qsort(left, poz - 1);
     qsort(poz + 1, right);
}

int main(){
    
    freopen("gutui.in","r", stdin);
    freopen("gutui.out","w",stdout);
    int i;
    
    scanf("%d%d%d", &N, &H, &U);
    for(i = 0; i < N; i++){
          scanf("%d", &h[i]);
          scanf("%d", &g[i]);
    }
    
    qsort(0, N);
    
    t[1] = g[0];
    int x, max = g[0];
    
    for( i = 1; i < N; i++){
         x = (H - h[i]) / U;
         for( j = min(i, x) + 1; j >= 1; j--)
              if(t[j - 1] + g[i] > t[j]){
                     t[j] = t[j - 1] + g[i];
                     if(t[j] > max)
                        max = t[j];
              }
    }
    
    printf("%d", max);  
          
    return 0;
}