program infoarena_fractii;
var i,j,k,n:longint;

function cmmdc(a,b:longint):boolean;
begin
while a<>b do
begin
if a>b then a:=a-b
       else b:=b-a;
end;
if a=1 then cmmdc:=true
       else cmmdc:=false;
end;

begin
assign(input,'fractii.in');
reset(input);
readln(n);
close(input);
k:=2*n-1;
for i:=2 to n do
 for j:=i+1 to n do
  begin
  if cmmdc(j,i) then begin k:=k+2; write(i,'/',j,' ');end;
  end;

assign(output,'fractii.out');
rewrite(output);
writeln(k);
close(output);
end.