program fractii;
var f,g:text;i,n,j,s:longint;
    v:array[1..1000001]of longint;
begin
   assign(f,'fractii.in');reset(f);
   assign(g,'fractii.out');rewrite(g);
     read(f,n);
     for i:=1 to n do v[i]:=i;
       for i:=2 to n do begin
         if v[i]=i then begin
           j:=i;
          while j<=n do begin
           v[j]:=v[j] div i;
           v[j]:=v[j]*(i-1);
           j:=j+i;
           end;
          end;
        end;
        for i:=1 to n do s:=s+v[i];
          write(g,s*2-1);
        close(f);close(g);
       end.