type arr=array[1..500,1..5] of integer;
     ar=array[1..500] of boolean;
var a:arr;
    d:ar;
    i,j,maxcode,max,n:integer;
function init(i,j:integer):boolean;
begin
  if (a[i,1]>a[j,1]) and (a[i,2]<a[j,2]) then init:=true
                                         else init:=false;
end;
procedure search(x:integer);
var i,j,m,mcode:integer;
begin
  m:=0;mcode:=0;
  for i:=1 to n do
  begin
    if init(i,x) then
        begin
          if d[i] then search(i);
          if a[i,3]>m then begin m:=a[i,3];mcode:=i;end;
        end;
  end;
  a[x,3]:=m+1;
  a[x,4]:=mcode;
  d[x]:=false;
end;
procedure printa(i:integer);
begin
  if a[i,4]<>0 then printa(a[i,4]);
  if i=maxcode then writeln(i)
               else write(i,' ');
end;
begin
  fillchar(d,sizeof(d),true);
  fillchar(a,sizeof(a),0);
  readln(n);
  if n=0 then begin writeln(0);halt;end;
  for i:=1 to n do
  begin
    readln(a[i,1],a[i,2]);
    if a[i,1]>a[i,2] then begin j:=a[i,1];a[i,1]:=a[i,2];a[i,2]:=j;end;
    a[i,3]:=1;
  end;
  max:=0;maxcode:=0;
  for i:=1 to n do
  begin
    if d[i] then search(i);
    if a[i,3]>maxcode then begin max:=a[i,3];maxcode:=i;end;
  end;
  i:=maxcode;
  writeln(max);
  printa(maxcode);
end.