The sum of the two numbers A and B is 33, the sum of the two numbers B and C is 44, and the sum of the two numbers C and D is 66, so what is the sum of the two numbers A and D?
甲乙两数之和是33，乙丙两数之和是44，丙丁两数之和是66，那么甲丁两数之和是多少．
<gadget id="calculator">33 + 66</gadget>
<output>99</output>

<gadget id="calculator">99 - 44</gadget>
<output>55</output>

<result>55</result>