var a:array[1..1000000]of int64;
    b:array[1..1000000]of boolean;
    n,i,j,k:longint; f:text;
begin
{ assign(f,'fractii.in');
 reset(f);}
 readln(n);
{ close(f);}
 for i:=1 to n do begin a[i]:=i; b[i]:=true; end;
 for i:=2 to n do
  if b[i] then
   begin
    j:=i;
    while j<=n do
     begin
      a[j]:=a[j]*(i-1)div i;
      b[j]:=false;
      j:=j+i;
     end;
   end;
 k:=0;
 for i:=1 to n do k:=k+a[i];
 {assign(f,'fractii.out');
 rewrite(f);}
 writeln(k*2-1);
{ close(f); }
 readln;
end.