There are many wonderful and interesting phenomena in natural numbers, and many secrets are waiting for us to explore! For example: for any natural number, now sum its digits, then multiply the sum by 3 and add 1, repeat this operation many times, the result of the operation will finally get a fixed number R, which will fall into A number "trap" can never be escaped. No natural number can escape its "claw". Then what is the fixed number R that finally falls into the "trap".
自然数中有很多奇妙而有趣的现象，很多秘密等待着我们去探索！比如：对任意一个自然数，现将其各位数字求和，再将其和乘以3后加上1，多次重复这种操作，运算结果会最终会得到一个固定的数R，它会掉入一个数字"陷阱"，永远也别想逃出来，没有一个自然数能逃出它的"魔掌"，那么最终掉入"陷阱"的这个固定不变的数R是多少．
<gadget id="calculator">1 + 0</gadget>
<output>1</output>

<gadget id="calculator">3 * 1</gadget>
<output>3</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">4 + 0</gadget>
<output>4</output>

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 + 1</gadget>
<output>13</output>

<result>13</result>