#include <bits/stdc++.h> using namespace std; long long ans,s, maxn, cnt, k, m, b[1000005], c[1000005]; long long n;

struct yyy{ int gd,lq; }a[100005];

bool cmp(yyy a,yyy b){ return a.lq<b.lq; }

int main() { // freopen("gold.in", "r", stdin); // freopen("gold.out", "w", stdout); cin>>n>>s; cin>>k>>m; m+=k; for(int i=1;i<=n;i++){ cin>>a[i].gd>>a[i].lq; } sort(a+1,a+n+1,cmp); for(int i=1;i<=n&&s>0;i++){ if(a[i].gd<=m&&a[i].lq<=s){ ans++; s-=a[i].lq; } } cout<<ans; return 0; }