此题数据有误……

是我英文太差，还是答案出错……

Program P2528;
const
   maxn=10000;
   maxr=10000000;
var
   t,n,i,j,k:longint;
   a,b,v:array[1..maxn*2] of longint;
   h:array[1..maxr] of longint;
   col:array[1..maxn*100] of longint;
   visit:array[1..maxn*2] of boolean;


procedure qsort(l,r:longint);
var
   i,j,m,p:longint;
begin
   i:=l;
   j:=r;
   m:=v[(l+r) div 2];
   repeat
      while v[i]<m do inc(i);
      while v[j]>m do dec(j);
      if i<=j then
      begin
         p:=v[i];
         v[i]:=v[j];
         v[j]:=p;
         inc(i);
         dec(j);
      end;
   until i>j;
   if l<j then qsort(l,j);
   if i<r then qsort(i,r);
end;
procedure update(l,r,sonl,sonr,root,color:longint);
var
   i,j,k,mid:longint;
begin
   mid:=(l+r) shr 1;
   if (sonl<=l) and (r<=sonr) then
   begin
      col[root]:=color;
      exit;
   end;

   if (col[root]>=0) then
   begin
      col[root*2]:=col[root];
      col[root*2+1]:=col[root];
      col[root]:=-1;
   end;
   if not((mid<sonl) or (sonr<l)) then update(l,mid,sonl,sonr,root*2,color);
   if not((r<sonl) or (sonr<mid+1)) then update(mid+1,r,sonl,sonr,root*2+1,color);



end;
function dfs(l,r,root:longint):longint;
var
   i,j,mid:longint;
begin
   mid:=(l+r) shr 1;
   if col[root]=0 then exit(0);
   if col[root]>0 then
   begin
      if not(visit[col[root]]) then
      begin
         visit[col[root]]:=true;
         exit(1);
      end
      else exit(0);
   end;

   exit(dfs(l,mid,root*2)+dfs(mid+1,r,root*2+1));

end;
begin
   read(t);
   while t>0 do
   begin
      dec(t);
      read(n);
      for i:=1 to n do
      begin
         read(a[i],b[i]);
         v[i]:=a[i];
         v[n+i]:=b[i];
      end;
      qsort(1,2*n);
      j:=1;
      for i:=2 to 2*n do
         if v[i]<>v[i-1] then
         begin
            inc(j);
            v[j]:=v[i];
         end;
      for i:=1 to j do h[v[i]]:=i;

      fillchar(col,sizeof(col),0);

      for i:=1 to n do
      begin
        update(1,j,h[a[i]],h[b[i]],1,i);
      end;
      fillchar(visit,sizeof(visit),false);
      writeln(dfs(1,j,1));

   end;
end.