program fractii;
var a,b,x,n,y,k:longint;
    f,g:text;
function cm(x,y:integer):longint;
var c,i,j:longint;
begin
if x<y then
       begin
       for i:=1 to x do
         if (y mod i = 0)and(x mod i = 0 ) then
           c:=i;
       end
       else
       if b<a then
       for i:=1 to b do
         if (x mod i = 0)and(y mod  i = 0) then
         c:=i;
cm:=c;
end;
begin{pp}
assign(f,'fractii.in');reset(f);
assign(g,'fractii.out');rewrite(g);
readln(f,n);
k:=0;
for a:=1 to n do
  for b:=1 to n do
    if (cm(a,b)=1) and (a<>b) then
    begin
    k:=k+1;
    writeln(a,' ',b);
    end;
write(g,k+1);
close(f);
close(g);
readln;
end.