include<iostream>

include<cstdio>

using namespace std;

int main(){

int b,n,s,a,x,count=0;
cin>>n>>s>>a>>b;
b=b+a;
for(int i=1;i<=n;++i){
    int x,y;
    cin>>x>>y;
    if(x <= b && (s-y) >= 0){
        count++;
        s-=y;
    }
    if(s<=0){
        break;
    }
}
cout<<count;

}