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