var fi,fo:text;
    rez,l,nr_div,n:int64;
    ct,i1,j1:longint;
    prime:array[1..1000000]of byte;
    m:array[0..1000000]of int64;
    primee:array[1..500000]of longint;
procedure gen(ba:int64);
var i,j:int64;
begin
  i:=3;
  primee[1]:=2;
  l:=1;
  prime[1]:=1;
  while i<=ba do
    begin
      if prime[i]=0 then
        begin
          j:=3*i;
          inc(l);
          primee[l]:=i;
          while j<=ba do
             begin
                prime[j]:=1; inc(j,i);
             end;
        end;
      inc(i,2);
    end;
end;
procedure prim(nr:int64);
var i:int64;
begin
  ct:=1; nr_div:=0; i:=1;
  if (nr=2)or((prime[nr]=0)and(nr and 1=1)) then
     begin
       inc(nr_div);
       exit;
     end;
  if (sqrt(nr)=trunc(sqrt(nr)))or(nr mod 4=0) then
     begin
       ct:=2;
       exit;
     end;
  while i<=l do
   if (nr mod primee[i]=0) then
     begin
       inc(nr_div);
       nr:=nr div primee[i];
       if nr=1 then exit;
       if nr mod primee[i] = 0 then
         begin
           ct:=2;
           exit;
         end;
       if prime[nr]=0 then
         begin
           inc(nr_div);
           exit;
         end;
       inc(i);
     end
   else inc(i);
end;
procedure verif(i:int64);
begin
  prim(i);
  if ct=1 then
    if nr_div and 1 = 1 then rez:=rez + (m[i]*(m[i]-1)) shr 1
                        else rez:=rez - (m[i]*(m[i]-1)) shr 1;
end;
begin
  assign(fi,'fractii.in'); reset(fi);
  assign(fo,'fractii.out'); rewrite(fo);
  readln(fi,n);
  rez:=0; m[0]:=1; m[1]:=1;
  gen(n shr 1);
  for i1:=2 to n do
    begin
      for j1:=1 to n div i1 do
         inc(m[i1]);
      if (m[i1]>0) then verif(i1);
    end;
  rez:=(n*(n-1)) shr 1 - rez;
  rez:=2*rez+1;
  writeln(fo,rez);
  close(fi); close(fo);
end.