Put several balls in four boxes A, B, C and D respectively. Box A has the most balls. Box A has 4 more balls than Box B. The difference between Box B and Box C is 3 balls. The difference between Box C and Box D is 2 balls. How many more balls are in Box A than the box with the least balls?
把若干个球分别放在甲乙丙丁四个盒子中．甲盒中球最多，甲盒比乙盒多4个球，乙盒与丙盒相差3个球，丙盒与丁盒相差2个球，甲盒比放球最少的盒子多放几个球？
<gadget id="calculator">4 + 3 + 2</gadget>
<output>9</output>

<result>9</result>