Select six numbers from the nine numbers 1-9 to form three two-digit prime numbers, and make the sum of these three prime numbers also a prime number, and the sum should be as small as possible. What is the sum of these three prime numbers?
从1-9九个数中选取六个数，组成三个两位数的质数，并使这三个质数的和也是质数，并且和要尽可能小，这三个质数的和是多少．
<gadget id="calculator">13 + 29 + 47</gadget>
<output>89</output>

<result>89</result>