var fi,fo:text;
    n,i,k,j:integer;
begin
  assign(fi,'tije.in'); reset(fi);
  assign(fo,'tije.out'); rewrite(fo);
  readln(fi,n);
  for i:=n-1 downto 1 do
    begin
      for k:=n+1 downto 2 do
        for j:=1 to i do
         writeln(fo,k-1,' ',k);
      for j:=1 to i do
        writeln(fo,n+1,' ',1);
    end;
  close(fi);
  close(fo);
end.