Grandpa is 78 years old this year, eldest grandson is 27 years old, second grandson is 23 years old, and third grandson is 16 years old. Ask how many years later the grandfather's age is equal to the sum of the ages of the three grandchildren.
今年爷爷78岁，长孙27岁，次孙23岁，三孙16岁．问多少年以后爷爷的年龄等于三个孙子的年龄之和．
<gadget id="calculator">78 - 27 - 23 - 16</gadget>
<output>12</output>

<gadget id="calculator">1 - 1</gadget>
<output>0</output>

<gadget id="calculator">1 + 1 + 0</gadget>
<output>2</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<result>6</result>