program pku2653;
type xd=record
          x1,y1,x2,y2:double;
        end;
     zx=record
          k,b:double;
        end;
     dot=record
           x,y:double;
         end;
var n,t,i,j:longint;
    a:array[0..100000]of xd;
    b:array[0..100000]of longint;
    p:xd;
function fc(a,b:dot):zx;
begin
  if a.x=b.x then
  begin
    fc.k:=1e10;
    fc.b:=a.x;
  end
  else
  begin
    fc.k:=(a.y-b.y)/(a.x-b.x);
    fc.b:=a.y-a.x*fc.k;
  end;
end;
function jd(l1,l2:zx):dot;
begin
  if l1.k=1e10 then exit(jd(l2,l1));
  if l2.k=1e10 then
  begin
    jd.x:=l2.b;
    jd.y:=l1.k*jd.x+l1.b;
    exit;
  end;
  jd.x:=(l2.b-l1.b)/(l1.k-l2.k);
  jd.y:=l1.k*jd.x+l1.b;
end;
function zai(d:dot;x:xd):boolean;
begin
  zai:=((d.x<=x.x1)and(d.x>=x.x2))or((d.x>=x.x1)and(d.x<=x.x2));
  zai:=zai and((d.y<=x.y1)and(d.y>=x.y2))or((d.y>=x.y1)and(d.y<=x.y2));
  if(d.x=x.x1)and(d.y=x.y1)then exit(false);
  if(d.x=x.x2)and(d.y=x.y2)then exit(false);
end;
procedure swap(var x,y:double);
var t:double;
begin
  t:=x;
  x:=y;
  y:=t;
end;
function xj(x,y:xd):boolean;
var d1,d2,d3,d4,d5:dot;
    x1,x2:zx;
begin
  d1.x:=x.x1;
  d1.y:=x.y1;
  d2.x:=x.x2;
  d2.y:=x.y2;
  d3.x:=y.x1;
  d3.y:=y.y1;
  d4.x:=y.x2;
  d4.y:=y.y2;
  x1:=fc(d1,d2);
  x2:=fc(d3,d4);
  if x1.k=x2.k then
  begin
    if x1.b<>x2.b then exit(false);
    if x1.k<1e10 then
    begin
      if d1.x>d2.x then swap(d1.x,d2.x);
      if d3.x>d4.x then swap(d3.x,d4.x);
      if d1.x>d3.x then
      begin
        swap(d1.x,d3.x);
        swap(d2.x,d4.x);
      end;
      if(d1.x<=d2.x)and(d2.x<=d3.x)and(d4.x>=d3.x)then exit(false)
      else exit(true);
    end
    else
    begin
      if d1.y>d2.y then swap(d1.y,d2.y);
      if d3.y>d4.y then swap(d3.y,d4.y);
      if d1.y>d3.y then
      begin
        swap(d1.y,d3.y);
        swap(d2.y,d4.y);
      end;
      if(d1.y<=d2.y)and(d2.y<=d3.y)and(d4.y>=d3.y)then exit(false)
      else exit(true);
    end;
  end;
  d5:=jd(x1,x2);
  xj:=zai(d5,x)and(zai(d5,y));
end;
begin
  repeat
    readln(n);
    if n=0 then halt;
    t:=0;
    for i:=1 to n do
    begin
      readln(p.x1,p.y1,p.x2,p.y2);
      for j:=t downto 1 do
      if xj(a[j],p)then
      begin
        a[j]:=a[t];
        b[j]:=b[t];
        dec(t);
      end;
      inc(t);
      a[t]:=p;
      b[t]:=i;
    end;
    write('Top sticks:');
    for i:=1 to t-1 do write(' ',b[i],',');
    writeln(' ',b[t],'.');
  until 0=1;
end.
试了n组数据都是对的
难道有什么陷阱？