//最长非降子序列 感觉思维还是有点僵化哦
#include <iostream>
#include <algorithm>
#include <stdio.h>
#include <set>
#include <queue>
#include <cstring>
#include <string>
#include <limits.h>
#include <string.h>
#include <vector>
#include <map>
#define LL long long
#define INF 2100000000
#define fi first
#define se second
#define lowbit(x) (x&(-x))
#define eps 5e-7
using namespace std;
const int maxn=(int)1e5 +10;
const int maxm=(int)2e4+10;
const LL MOD=(LL)1e9+7;
int n;LL r,w,h;
LL a,b;
struct nod{
LL x,y;
void in(){
scanf("%I64d%I64d",&a,&b);
x=b-r*a;y=b-r*(w-a);
}
};
bool cmp(const nod&a,const nod&b){
return (a.y==b.y&&a.x<b.x )||a.y<b.y;
}
nod f[maxn];
vector<LL> q;
int main()
{
#ifdef shuaishuai
freopen("C:\\Users\\hasee\\Desktop\\a.txt","r",stdin);
//freopen("C:\\Users\\hasee\\Desktop\\b.txt","w",stdout);
#endif
scanf("%d%I64d%I64d%I64d",&n,&r,&w,&h);
for(int i=0;i<n;i++) f[i].in();
sort(f,f+n,cmp);
q.reserve(n);
q.push_back(f[0].x);
for(int i=1;i<n;i++){
if(q.back()<=f[i].x) q.push_back(f[i].x);
else
*upper_bound(q.begin(),q.end(),f[i].x)=f[i].x;
}
printf("%d\n",q.size());
return 0;
}
