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