#include <bits/stdc++.h>
using namespace std;
const int N=1e5;
struct pp{
	int x,y;
}apple[N];
bool cmp(pp x,pp y){
	return x.y<y.y;
}
int n,s,a,b,c,num=0;
int main(){
	cin>>n>>s;
	cin>>a>>b;
	c=a+b;
	for(int i=1;i<=n;i++){
		cin>>apple[i].x>>apple[i].y;
	}
	sort(apple+1,apple+1+n,cmp);
	for(int i=1;i<=n;i++){
		if(s<0){
			break;
		}
		if(c>=apple[i].x){
			num++;
			s-=apple[i].y;
		}
		
	}
	cout<<num-1;
	return 0;
}