#include<iostream>
#include<algorithm>
#include<cstdio>
#include<set>
#pragma GCC optimize("Ofast")
using namespace std;
const int N=1e5+5;
int XX,n,num;
struct mount
{
  double k,b;
  int x1,y1,x2,y2;
  double fc(){return k*XX+b;}
}m[N];
struct note
{
  int x,y,id; bool flag;
  bool operator<(note b)const
  {
    return x<b.x;
  }
}tot[N<<1];
struct cmp
{
  bool operator()(mount a,mount b)
  {
    return a.fc()<b.fc();
  }
};set<mount,cmp> s;
int main()
{
  ios::sync_with_stdio(0),cin.tie(0);
  cin>>n; int ans=1;
  for(int i=1;i<=n;++i)
    {
      int x1,y1,x2,y2; cin>>x1>>y1>>x2>>y2;
      double k=double(y2-y1)/(x2-x1),b=y1-k*x1;
      m[i]={k,b,x1,y1,x2,y2}; tot[++num]={x1,y1,i,0}; tot[++num]={x2,y2,i,1};
    }
  sort(tot+1,tot+1+num); auto now=m[1];
  for(int i=1;i<=num;++i)
    {
      XX=tot[i].x;
      if(now.x2==tot[i].x)
        {
          while(tot[i].x==now.x2)
            {
              if(tot[i].y!=now.y2)
                {
                  //if(!tot[i].flag)s.insert(m[tot[i].id]);
                  //else s.erase(m[tot[i].id]);
                   (!tot[i].flag)?(s.insert(m[tot[i].id])):(s.erase(m[tot[i].id]));
                }
              ++i;
            }
          auto nxt=s.lower_bound(now);
          if(nxt==s.begin())break; 
          --nxt; ++ans; s.erase(now); now=*nxt; --i;
        }
      else
        {
          if(!tot[i].flag)s.insert(m[tot[i].id]);
          else s.erase(m[tot[i].id]);
        }
    }
  cout<<ans<<'\n';
  return 0;
}

这个代码中的这个部分用不了

 while(tot[i].x==now.x2)
            {
              if(tot[i].y!=now.y2)
                {
                  //if(!tot[i].flag)s.insert(m[tot[i].id]);
                  //else s.erase(m[tot[i].id]);
                  (!tot[i].flag)?(s.insert(m[tot[i].id])):(s.erase(m[tot[i].id]));
                }
              ++i;
            }

应该如何解决