var v:array [1..1000000] of longint;
    i, j, n:longint;
    sum:int64;
    f, g:text;

begin
assign (f, 'fractii.in'); reset (f);
assign (g, 'fractii.out'); rewrite (g);
read (f, n);
for i := 1 to n do v[i]:=i;

i:=2;
while i <= n do
  begin
  if v [i] = i then
    begin
    j:=i;
    while j <= n do
      begin
      v[j]:=v[j]- v[j] div i;
      j:=j+i;
      end;
    end;
  i:=i+1;
  end;


for i := 1 to n do sum := sum + v[i];

sum:=sum*2-1;
writeln (g, sum);
close (f); close (g);
end.