1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstdio>
 4 #include<cstdlib>
 5 #include<cmath>
 6 #include<cstring>
 7 using namespace std;
 8 const int INF=0x3f3f3f3f;
 9 const int MAXN=100010;
10 struct Node{
11     int x,h;
12     double s;
13 };
14 Node dt[MAXN];
15 int cmp(Node a,Node b){
16     return a.x<b.x;
17 }
18 int main(){
19     int N;
20     int T,A;
21     double ang;
22     while(scanf("%d",&N),N){
23         for(int i=0;i<N;i++){
24             scanf("%d%d",&dt[i].x,&dt[i].h);
25         }
26         scanf("%d/%d",&T,&A);
27         ang=1.0*T/A;
28         for(int i=0;i<N;i++)dt[i].s=dt[i].h/ang;
29         sort(dt,dt+N,cmp);
30         int num=0;
31         double t=0;
32         for(int i=0;i<N;i++){
33             if(dt[i].x+dt[i].s>t)t=dt[i].x+dt[i].s;
34             else num++;
35         }
36         printf("%d\n",N-num);
37     }
38     return 0;
39 }