program ia;
	
var
	i,j,n:longint;
	phi:array[1..1000000] of longint;
	res:uint64;
	fIn,fOut:text;
	
begin
	assign(fIn,'fractii.in'); reset(fIn);
	assign(fOut,'fractii.out'); rewrite(fOut);
	readln(fIn,n);
	res:=1;
	for i:=1 to n do
		phi[i]:=i-1;
	for i:=2 to n do begin
		j:=i*2;
		while (j<=n) do begin
			phi[j]:=phi[j]-phi[i];
			j:=j+i;
		end;
		res:=res+2*phi[i];
	end;
	writeln(fOut,res);
	close(fIn); close(fOut);
end.