#include<bits/stdc++.h>
using namespace std;
int n,s,a,b,sum;
struct t{
	int x,y;
}k[5005];
bool cmp(t w,t z){
	return w.y<z.y;
}
int main(){
	cin>>n>>s>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>k[i].x>>k[i].y;
	}
	sort(k+1,k+1+n,cmp);
	for(int i=1;i<=n;i++){
		if(a+b>=k[i].x&&s>=k[i].y){
			sum++;
			s-k[i].y;
		}
	}
	cout<<sum;
	return 0;
}