program t1078;
const
  maxn=500;
type
  tnode=record
    x,y:integer;
  end;
var
  p:array[1..maxn] of tnode;
  v:array[1..maxn] of integer;
  f:array[1..maxn] of integer;
  pre:array[1..maxn] of integer;
  n,i,j:integer;

procedure init;
var
  i,j,y:integer;
  x:tnode;
begin
  for i:=1 to n do v[i]:=i;
  for i:=1 to n do
   for j:=i+1 to n do
    if p[i].y>p[j].y then begin
       x:=p[i];
       p[i]:=p[j];
       p[j]:=x;
       y:=v[i];
       v[i]:=v[j];
       v[j]:=y;
    end;
end;

procedure dynamic;
var
  i,j,k:integer;

  procedure outans(i:integer);
  begin
    if i<>0 then begin
       outans(pre[i]);
       write(v[i],' ');
    end;
  end;
begin
  fillchar(f,sizeof(f),0);
  fillchar(pre,sizeof(pre),0);
  f[1]:=1;pre[1]:=0;
  for i:=2 to n do
   for j:=1 to i-1 do
    if (p[j].x>p[i].x) and (f[j]+1>f[i]) then begin
       f[i]:=f[j]+1;
       pre[i]:=j;
    end;
  j:=1;k:=f[1];
  for i:=2 to n do if k<f[i] then begin
      k:=f[i];
      j:=i;
  end;
  writeln(k);
  outans(pre[j]);
  writeln(v[j]);
end;

begin
  //assign(input,'in');reset(input);
  readln(n);
  if n=0 then begin
   writeln(0);
   halt;
  end;
  for i:=1 to n do begin
   readln(p[i].x,p[i].y);
   if p[i].x>p[i].y then begin
      j:=p[i].x;
      p[i].x:=p[i].y;
      p[i].y:=j;
   end;
  end;
  init;
  dynamic;
end.

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