!752

p {
  makeBot("Add Bot.");
}

static S answer(S s) {
  L<S> tok = javaTok(s);
  int i;
  Long result = null;
  while ((i = matchMeta(tok, "<number>", "+", "<number>")) >= 0) {
    long a = parseLong(tok.get(i)), b = parseLong(tok.get(i+4));
    result = a+b;
    clearAllTokens(tok.subList(i, i+5));
    tok.set(i, "" + result);
    tok = javaTok(tok);
  }
  if (result != null) ret "" + result;
  ret null;
}