#include<bits/stdc++.h>
using namespace std;
struct s
{
	long long x,y,c;
}su[10000009];
bool cmp(s a,s b)
{
	a.c<b.c;
}
int main()
{
	long long n,s,a,b,sum=0;
	cin>>n>>s;
	cin>>a>>b;
	for(int i=0;i<n;i++){
	cin>>su[i].x>>su[i].y;
	su[i].c=su[i].x/su[i].y;
	}
	sort(su,su+n,cmp);
	for(int i=0;i<n;i++)
	{
		if((a+b)<=su[i].x){
		if(s>=0){
		s-=su[i].y;
		sum++;
	}
}
	else 
	break;
	}
	cout<<sum;
	return 0;
}