#include <iostream>
using namespace std;
int main(){
	int x[300] = {},y[110] = {},n,s,a,b,ans = 0;
	cin >> n >> s >> a >> b;
	for(int i = 1;i <= n;i++){
		cin >> x[i] >> y[i];
	}
	b += a;
	for(int i = 1;i <= n;i++){
		if(b >= x[i] && s >= y[i]){
			ans++;
			s--;
		}
	}
	cout << ans;
	return 0;
}