var n,i,s:longint;
    f,g:text;
function euler(x:longint):longint;
var p,i,j:longint;
    b:boolean;
begin
     p:=x;
     if x mod 2=0 then p:=p div 2;
     if x=2 then p:=1
     else if x=3 then p:=2
     else if x=4 then p:=2
     else if x=5 then p:=4
     else begin
          for i:=3 to {trunc(sqrt(}x{))+1} do
              if x mod i=0 then begin
                 j:=1;
                 b:=true;
                 while (j<i-1) and (b=true) do begin
                       j:=j+1;
                       if i mod j=0 then b:=false;
                 end;
                 if b=true then p:=p*(i-1) div i;
              end;
     end;
     euler:=p;
end;
begin
     assign(f,'fractii.in');
     reset(f);
     readln(f,n);
     close(f);
     for i:=1 to n do s:=s+euler(i)*2;
     assign(g,'fractii.out');
     rewrite(g);
     writeln(g,s-1);
     close(g);
end.