var n,i,j,k:longint;
    v:array[1..1000000] of longint;
    f,g:text;
begin
assign(f,'fractii.in');
assign(g,'fractii.out');
reset(f);
rewrite(g);
read(f,n);
k:=0;
for i:=1 to n do v[i]:=i;
for i:=2 to n do
        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;
for i:=1 to n do k:=k+v[i];
write(g,(k*2-1));
close(f);
close(g);
end.