记录编号	8362	评测结果	AAAAAAAAAAA
题目名称	[BYVoid S3] 彩色穿孔卡片	最终得分	100
用户昵称	Achilles	是否通过	通过
代码语言	Pascal	运行时间	0.109 s
提交时间	2008-11-13 19:10:54	内存使用	0.24 MiB

program punch;
var
  sz:array[0..10000]of record
    b,e,c:longint;
  end;
  hx:array[1..10000]of 0..1;
  n,m,i,j,t1,t2,t:longint;
begin
  fillchar(hx,sizeof(hx),0);
  assign(input,'punch.in');
  assign(output,'punch.out');
  reset(input);
  rewrite(output);
  readln(n);
  m:=0;
  for i:=1 to n do
  begin
     readln(t1,t2);
    t:=0;
    while t<m do
    begin
      t:=t+1;
      if (sz[t].b>=t1)and(sz[t].e<=t2) then begin
        sz[t]:=sz[m];
        m:=m-1;
        t:=t-1;
      end
      else begin
        if (sz[t].b<t1)and(sz[t].e>t2) then begin
          m:=m+1;
          sz[m]:=sz[t];
          sz[t].e:=t1;
          sz[m].b:=t2;
        end
        else begin
          if (t1<=sz[t].b)and(sz[t].b<=t2)and(t2<sz[t].e) then begin
            sz[t].b:=t2;
          end
          else begin
            if (sz[t].b<t1)and(t1<=sz[t].e)and(sz[t].e<=t2) then begin
              sz[t].e:=t1;
            end;
          end;
        end;
      end;
    end;
    m:=m+1;
    sz[m].b:=t1;
    sz[m].e:=t2;
    sz[m].c:=i;
  end;
  t:=0;
  for i:=1 to m do
    if (hx[sz[i].c]=0)and(sz[i].b<sz[i].e) then begin
      t:=t+1;
      hx[sz[i].c]:=1;
    end;
  writeln(t);
  close(input);
  close(output);
end.