var f,g:text;
    cnt,n,i:longint;
    e{uler}:array[1..1000001] of longint;
procedure fi;
var i,j:longint;
begin
for i:=1 to n do e[i]:=i;
for i:=2 to n do
 if e[i]=i then
  begin
   j:=i;
   while j<=n do
    begin
     e[j]:=e[j] div i;
     e[j]:=e[j]*(i-1);
     j:=j+i;
    end;
 end;
end;

BEGIN
cnt:=0;
assign(f,'fractii.in');reset(f); readln(f,n);
assign(g,'fractii.out');rewrite(g);
fi;
 for i:=2 to n do
  cnt:=cnt+e[i];
cnt:=cnt*2+1;
write(g,cnt);
close(f);close(g);
END.