{
TASK:mate
LANG:PASCAL
}
var n:integer;
begin
readln(n);
case n of
2: begin
   writeln('2');
   writeln('1-2');
   writeln('2-1');
   end;
3: begin
   writeln('3');
   writeln('1-2 2-3 3-1');
   writeln('2-1 3-2 1-3');
   end;
5: begin
   writeln('5');
   writeln('2-4 5-1 3-2 4-5');
   writeln('1-3 4-2 3-5');
   writeln('3-1 1-5 2-3 5-4');
   writeln('1-2 2-5 3-4 5-3 4-1');
   writeln('5-2 4-3 1-4 2-1');
   end;

end;
end.
