static <A> int lcLength(LineCompedSingle<A> lc) {
  int n = 0;
  for (int symbol : lc.main)
    n += lcLength(lc, lc.main);
  ret n;
}
  
static <A> int lcLength(LineCompedSingle<A> lc, int symbol) {
  if (symbol < l(lc.literals))
    ret 1;
  else {
    IntPair pair = lc.pairs.get(idx-l(lc.literals)));
    ret lcLength(lc, pair.a) + lcLength(lc, pair.b);
  }
}