#include<iostream>
#include<algorithm>
using namespace std;
int n,s,a,b,ans;
struct pos
{
	int x,y;
}c[5005];
bool cmp(pos a,pos b)
{
	a.y<b.y;
}
int main()
{
	cin>>n>>s>>a>>b;
	for(int i=1;i<=n;i++)
	{
		cin>>c[i].x>>c[i].y;
	}
	sort(c+1,c+n+1,cmp);
	for(int i=1;i<=n;i++)
	{
		if(a+b>=c[i].x&&s>=c[i].y)
		{
			s-=c[i].y;
			ans++;
		}
		else if(s<c[i].y)
		{
			break;
		}
	}
	cout<<ans<<endl;
	return 0;
}

不懂为什么TLE+MLE