code: private BigDecimal parseLargePair(final NumberBuffer buffer) {
          final BigDecimal first = parseMediumNumber(buffer);
          final BigDecimal second = parseLargeKanjiNumeral(buffer);
  
          if (first == null && second == null) {
              return null;
          }
  
          if (second == null) {
              // If there's no second factor, we return the first one
              // This can happen if we our number is smaller than 10,000 (万)
              return first;
          }
  
          if (first == null) {
              // If there's no first factor, just return the second one,
              // which is the same as multiplying by 1, i.e. with 万
              return second;
          }
  
          return first.multiply(second);
      }
docs: Parses a pair of large numbers, i.e. large kanji factor is 10,000（万）or larger
  
  @param buffer buffer to parse
  @return parsed pair, or null on error or end of input