type vector=array[1..1000000] of longint;
var rez:int64;
    n,i,j:longint;
    f,g:text;
    t:vector;
begin
        assign(f,'fractii.in'); reset(f);
        assign(g,'fractii.out'); rewrite(g);
        readln(f,n);
        for i:=1 to n do t[i]:=i;
        for i:=2 to n do
             if t[i]=i then
                begin
                j:=i;
                while j<=n do
                       begin
                       t[j]:=t[j] div i;
                       t[j]:=t[j] * (i-1);
                       j:=j+i;
                       end;
                end;
        rez:=1;
        for i:=2 to n do begin
                      rez:=rez + 2 * t[i];
                      end;
        write(g,rez);
        close(f); close(g);
end.