#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int N = 100001;

struct Posi{
    double x, y;
}Num[N];

bool cmp(Posi x, Posi y){
    return x.x < y.x;    
}

int main(){
    int T;
    while(~scanf("%d", &T), T){
        for(int i = 0; i < T; i++)
            scanf("%lf%lf", &Num[i].x, &Num[i].y);
        double tana, tanb;
        scanf("%lf/%lf", &tana, &tanb);
        sort(Num, Num+T, cmp);     //按位置排一下序。 
        double Max = Num[0].y; 
        int sum = 0;
        for(int i = 1; i < T; i++){
            if(Max-Num[i].y-(Num[i].x-Num[i-1].x)*tana/tanb >= 0){  //更新Max值及计算被挡木条数目； 
                sum++;                             
                Max = Max - (Num[i].x-Num[i-1].x)*tana/tanb;
            }
            else
                Max = Num[i].y;
        }
        printf("%d\n", T-sum);
    }
    return 0;
}