var f,g:text;
    x,y,x2,i:longint;
function cmmdc(a,i1:longint):boolean;
var ok:boolean;
    r:longint;
begin
      ok:=false;
      while(i1<>0)do
          begin
               r:=a mod i1;
               a:=i1;
               i1:=r;
          end;
      if a=1 then ok:=true;
end;

begin
     assign(f,'sum.in');
     assign(g,'sum.out');
     reset(f);
     rewrite(g);
{-rezolvarea problemei------------------------------}
     read(f,x);
     x2:=2*x;
     y:=0;
     for i:=1 to x2 do
         if cmmdc(x,i) then y:=y+i;
     write(g,y);

{---------------------------------------------------}
     close(g);
     close(f);
end.