#include<bits/stdc++.h>
using namespace std;
struct a{
	int gd;
	int lq;
}apple[1000];
bool comp(struct a x,struct a y){
	return x.lq>y.lq;
}
int main(){
	int n,s,a,b,ans=0;
	cin>>n>>s;
	cin>>a>>b;
	for(int i=0;i<n;i++){
		cin>>apple[i].gd;
		cin>>apple[i].lq;
	}sort(apple,apple+n,comp);
	for(int i=0;i<n;i++){
		if(s-apple[i].lq>0){
			if(apple[i].gd<=b||apple[i].gd<=a+b){
				ans++;
				s-=apple[i].lq;
			}
		}
	}cout<<ans;
	return 0;
}