import "io"

let digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVXYZ";

let print(n, b) be
{ let rest = n / b, left = n rem b;
  if n >= b then
    print(rest, b);  /* this is position A */
  outch(byte left of digits) }

let coll(x) be
{ let nexto = 3 * x + 1, nexte = x / 2;
  let odd = x rem 2 = 1;
  print(x, 7);   /* this is position B */
  if x = 1 then
  { outch ('\n');
    return }
  outch(' ');
  test odd then
    coll(nexto)  /* this is position C */
  else
    coll(nexte)  /* this is also position C */ }

let start() be
{ let s = 11;
  coll(s)       /* this is position D */ }