#include<bits/stdc++.h>
using namespace std;
double n,s,a,b,x[5005],y[5005],ans=0;
int main(){                        
    cin>>n>>s>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>x[i]>>y[i];
		s-=y[i];
		if(s>0 && a+b>=x[i] && s-y[i]>=0)
			ans+=1;
	}
	cout<<ans;            
    return 0;                       
}