一个字：帅

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n,k,a,b,xiaomajun_mizhi_shengao,ans=0;
struct Appel{
	ll x,y;
}xy[5010];
bool operator <(Appel x,Appel y){
	if(x.x>xiaomajun_mizhi_shengao || y.x>xiaomajun_mizhi_shengao) return x.x<y.x;
    else return x.y<y.y;
}
int main(){
	cin>>n>>k>>a>>b;
	xiaomajun_mizhi_shengao=a+b;
	for(ll i=1;i<=n;i++){
		cin>>xy[i].x>>xy[i].y;
	}
	sort(xy+1,xy+1+n);
	for(ll i=1;xy[i].x<=xiaomajun_mizhi_shengao;i++){
        if(xy[i].y>k)break;
        k-=xy[i].y;
		ans++;
	}
	cout<<ans;
	return 0;
}