请问为什么一个点WA还有2个运行错误呢？

#include<bits/stdc++.h>
using namespace std;
int n,m,a,b;
int cnt=0;
int s;
int ans;
struct node{
    int x;
    int y;
}apple[50005]; 
int r1,r2;
bool cmp(const node &aa,const node &bb)
{
    if(aa.y!=bb.y)
        return aa.y<bb.y;
}
int main()
{
    cin>>n>>s;
    cin>>a>>b;
    for(int i=1;i<=n;i++)
    {
        cin>>r1>>r2;
        if(r1<=a+b)
        {
            cnt++;
            apple[cnt].x=r1;
            apple[cnt].y=r2;
        }
    }
    sort(apple+1,apple+n+1,cmp);
    for(int i=1;i<=min(n,cnt);i++)
    {
        if(s>apple[i].y)
        {
            ans++;
            s-=apple[i].y;
        }
        if(s<apple[i].y)
        {
            cout<<ans<<endl;
            return 0;   
        }
    }
    cout<<ans<<endl;
    return 0;
}

求教