i := 1;
kw := 4;
while
    kw <= n
  do
  (i := 2*i;
   kw := 4*kw
  )
r := i;
dri := kw div2;
ik := dri div2;
while
     i > 1
  do
  (i := i div2;
   ik := (ik div2) div2;
   dri := dri div2;
   if (kw - dri - 3*ik)<=  n
   then
      r := r + i;
      dri := dri + 2*ik
   else
      kw := kw - dri - 3*ik;
  )