直接代码、、、

#include<string.h>

#include<stdio.h>

#include<queue>

#include<iostream>

#include<algorithm>

using namespace std;

struct node

{

    int fuel,dist;

    //bool operator < (const node&d) const{

     // return  dist>d.dist;

   // }

}s[10005];

bool cmp(node b,node c)

{

    return b.dist>c.dist;

}

int main()

{

    int a,l,p,pos,ans,d,fuels;

    scanf("%d",&a);

    priority_queue<int> q;

    for(int i=0;i<a;i++)

    {

        scanf("%d %d\n",&s[i].dist,&s[i].fuel);

    }

    sort(s,s+a,cmp);//从大到小进行排序，

    scanf("%d %d",&l,&p);

    s[a].dist=0;

    for(int i=0;i<=a;i++)

        s[i].dist=l-s[i].dist;

    fuels=p;

    ans=0;

    pos=0;

    for(int i=0;i<=a;i++)

    {

        d=s[i].dist-pos;

        while(fuels-d<0)

        {

            if(q.empty())

            {

                printf("-1\n");

                return 0;

            }

            fuels+=q.top();

            q.pop();

            ans++;

        }

        fuels-=d;

        pos=s[i].dist;

        q.push(s[i].fuel);

    }

    printf("%d\n",ans);

    return 0;

}