#include<iostream>
#include<algorithm>
using namespace std;
int n,s,a,b,x[1010],y[1010],ans;
bool cmp(int a,int b){
	return a<b;
}
int main(){
	cin>>n;
	cin>>s>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>x[i];
		cin>>y[i];
	}
	sort(y,y+1+n,cmp);
	for(int i=1;i<=n;i++){
		if(a+b>=x[i]){
		s-=y[i];
		ans++;
		}
		if(s<0){
			break;
		}
	}
	cout<<ans;
	return 0;
}

20分求调