program fractii;
var v:array[0..5000] of byte;
    b:array[0..5000] of longint;
    i,j,s,n,m,nr,x,y,p:longint;
    ok:boolean;
    a:array[0..1000000] of longint;
    f,g:text;
procedure ciur;
var i,j:longint;
begin
  i:=1;
  while ((i*i) shl 1)+(i shl 1) <= n do begin
    if ((v[i shr 3] shr (i and 7)) and 1 )=0 then begin
      j:=((i*i) shl 1)+ (i shl 1);
      while 2*j+1<=n do begin
        v[j shr 3]:=v[j shr 3] or (1 shl (j and 7));
        j:=j +(i shl 1)+1;
      end;
    end;
    inc(i);
  end;
  b[0]:=1; b[1]:=2;
  for i:=1 to n do
    if ((v[i shr 3] shr (i and 7)) and 1)=0 then
      if (2*i+1<=n) then begin
        inc(b[0]); b[b[0]]:=2*i+1;
      end;
end;

begin
 assign(f,'fractii.in'); reset(f);
 assign(g,'fractii.out'); rewrite(g);
 readln(f,m); n:=1000;
 a[1]:=1;
 ciur; s:=1;
 for i:=2 to m do begin
   j:=1; ok:=false; x:=i;
   while (ok=false)and(trunc(sqrt(i))>=b[j]) do begin
      p:=1; nr:=0;
      while (x mod b[j]=0) and(b[j]<=trunc(sqrt(i))) do begin
        p:=p*b[j]; inc(nr);
        x:=x div b[j];
        ok:=true;
      end;
      inc(j);
   end;
   { phi[p^e] = (p-1) * p^(e-1); phi[2^4] = 1 * 2^3; }
   { phi[a*p^e] = phi[a] * phi[p^e] = phi[a] }
   { phi[i] = phi[x * p^e] = phi[x] * (p-1) * p^(e-1) }
   if x=i then a[i]:=x-1
   else{ if (x=1)then }a[i]:=a[x] * (b[j-1]-1)*(p div b[j-1] );
                {else a[i]:=a[x] * a[p];}
   s:=s +2*a[i];
 end;
 writeln(g,s);
 close(g); close(f);
end.