There are three consecutive two-digit numbers, the ones digit of their sum is 1, and the tens digit is 3. What is the sum of these three natural numbers?
有三个连续的两位数，它们的和的个位数字是1，十位数字是3．那么这三个自然数的和是多少．
<gadget id="calculator">76 + 77 + 78</gadget>
<output>231</output>

<result>231</result>