#include<bits/stdc++.h>
using namespace std;
int ans,n,s,c1,d,a[1000005],b[1000005],c[1000005];
bool cmp(int a,int b){
	return a<b;
}
int main() {
	cin>>n>>s>>c1>>d;
	for (int i=1; i<=n; i++) cin>>a[i]>>b[i];
	for (int i=1; i<=n; i++) b[i]=b[i]*1000+i;
	c1+=d;
	sort(b+1,b+n+1,cmp);
	for (int i=1; i<=n; i++) c[i]=b[i]%1000;
	for (int i=1; i<=n; i++) b[i]/=1000;
	for (int i=1; i<=n; i++) {
		if(s<0) break;
		if(a[c[i]]<=c1&&s>=b[i]) {
			ans++;
			s-=b[i];
		}
	}
	cout<<ans;
	return 0;
}