var a:array[1..1010]of integer;
    n,i,j,z,q,x:integer;
begin
     assign(input,'dame.in');
     reset(input);
     assign(output,'dame.out');
     rewrite(output);
     readln(n);
     if n=2 then
     begin
          writeln(1);
          writeln(1,' ',1);
     end;
     if n=3 then
     begin
          writeln(2);
          writeln(1,' ',1);
          writeln(3,' ',2);
     end;


close(output);
end.