{
TASK:mate
LANG:PASCAL
}
var
   n : LongInt;
begin
readln(n);
if n=2
 then
  begin
   writeln('2');
   writeln('1-2');
   writeln('2-1');
  end;
if n=3
 then
  begin
   writeln('4');
   writeln('1-2 3-1 2-3');
   writeln('2-1 1-3 3-2');
   writeln('1-3');
   writeln('3-1');
  end;
if n=5
 then
  begin
   writeln('5');
   writeln('1-2 3-4 5-1');
   writeln('1-3 2-4 3-5 4-1 5-2');
   writeln('1-4 2-5 3-1 4-2 5-3');
   writeln('1-5 2-1 3-2 4-3 5-4');
   writeln('2-3 4-5');
  end;
if n=4
 then
  begin
   writeln('1-2 3-4 4-1 2-3');
   writeln('2-1 4-3 1-4 3-2');
   writeln('1-3 2-4');
   writeln('3-1 4-2');
  end;
end.