program p1;
var i,n,x,d,e,y,l,j,nr:int64;
    a:array[1..1000000] of longint;
    f,g:text;
begin
     assign(f,'fractii.in');reset(f);
     assign(g,'fractii.out');rewrite(g);
     read(f,n);
     a[1]:=1;
     nr:=1;
     for i:=2 to n do
         begin
              d:=2;
              x:=i;
              e:=0;
              y:=x;
              while x mod d>0 do d:=d+1;
              while y mod d=0 do
                    begin
                         e:=e+1;
                         y:=y div d;
                    end;
              l:=1;
              for j:=1 to e-1 do
                  l:=l*d;
              a[i]:=a[y]*(d-1)*l;
          end;
     for i:=2 to n do  nr:=nr+2*a[i];
     writeln(g,nr);
     close(f);
     close(g);
end.