// i must point at the (possibly imaginary) opening bracket ("{")
// index returned is index of closing bracket + 1 (or l(cnc))
static int findEndOfBlock(List<String> cnc, int i) {
  int j = i+2, level = 1, n = cnc.size();
  while (j < n) {
    S t = cnc.get(j);
    if ("{".equals(t)) ++level;
    else if ("}".equals(t)) --level;
    if (level == 0)
      return j+1;
    j += 2;
  }
  return n;
}