docs: private static int integerPart(String dirtyString) {
      int start = 0;
  
      while (start < dirtyString.length() && !Character.isDigit(dirtyString.charAt(start))) {
        ++start;
      }
  
      int end = start;
      while (end < dirtyString.length() && Character.isDigit(dirtyString.charAt(end))) {
        ++end;
      }
  
      if (start == end) {
        return 0;
      }
  
      return Integer.parseInt(dirtyString.substring(start, end));
    }