var i,n,k,j:longint;
    v:array[1..1000000] of longint;
    f,g:text;
begin
assign(f,'fractii.in');assign(g,'fractii.out');
reset(f);rewrite(g);
read(f,n);
close(f);
k:=0;
for i:=1 to n do
v[i]:=i;
for i:=2 to n do
if(v[i]=i) then begin
j:=i;
while(j<=n) do begin
v[j]:=v[j] div i;
v[j]:=v[j]*(i-1);
j:=j+i;
end;
end;
for i:=2 to n do k:=k+v[i];
writeln(g,2*k+1);
close(g);
end.