#include<bits/stdc++.h>
using namespace std;
struct A{
    int x,y;
    bool operator <(const A b){
        return y>b.y;
    }
};
int main(){
    int n,s,b,b1;
    cin>>n>>s;
    cin>>b>>b1;
    b=b+b1;
    A a[10000000];
    for(int i=0;i<n;i++){
        cin>>a[i].x>>a[i].y;
    }
    sort(a,a+n);
    int sun=0;
    for(int i=0;i<n;i++){
        if(a[i].y<=s&&a[i].x>=b){
            sun++;
            s-=a[i].y;
        }
        if(s==0){
            cout<<sun;
            return 0;
        }
    }
    cout<<sun;
}