var f,g:text;
    suma:qword;
    i,j,n,x:longint;
    v:array[0..1000001] of longint;
begin
assign(f,'fractii.in');reset(f);
assign(g,'fractii.out');rewrite(g);
read(f,n);
//construiesc v[i]
//asemenea ciurului lui eratostene
for i:=1 to n do v[i]:=i-1;
suma:=0;
for i:=2 to n do begin
 x:=i*2;
 while x<=n do begin
  v[x]:=v[x]-v[i];
  x:=x+i;
 end;
 suma:=suma+v[i];
end;
suma:=2*suma+1;
writeln(g,suma);
close(f);
close(g);
end.