var i,j,doi,jum,n:longint;
    rez:qword;
    k:longword;
    f,g:text;
begin
assign(f,'fractii.in');reset(f)
assign(g,'fractii.out');rewrite(g);
readln(f,n);
rez:=1;jum:=n div 2;
 for i:=2 to jum do phi[i]:=i-1;
 for i:=2 to jum do
  begin
   k:=phi[i];
   doi:=2*i;
   j:=3*i;
    while (j<=jum) do
     begin
      dec(phi[j],k);
      inc(j,doi);
     end;
    while (j<=n) do
     begin
     dec(phi[j],k);
      inc(j,doi);
     end;
  end;
rez:=rez+int64(n-1)*n div 2-int64(jum-1)*jum div 2;
writeln(g,2*rez-1);
end.