There are 21 pieces of chocolate. Five people A, B, C, D, and E ate up the chocolates in turn, but they don't know the order in which they ate them. A said: "I ate two-thirds of the remaining chocolate." B said: "I ate half of the remaining chocolate," said: "I ate half of the remaining chocolate." D said: "I ate up the rest of the chocolate," E said, "each of us eats a different amount." It is known that the amount each person eats is a positive integer. May I ask: How many pieces of chocolate did E eat?
现有21块巧克力，A、B、C、D、E五个人轮流把这些巧克力吃光了，但不知道他们吃的先后顺序．A说："我吃了剩下巧克力数量的三分之二．"B说："我吃了剩下巧克力数量的一半，"说："我吃了剩下巧克力数量的一半．"D说："我吃光了剩下的巧克力，"E说："我们每人吃的数量互不相同．"已知每人吃的数量都是正整数，请问：E吃了多少块巧克力？
<gadget id="calculator">21 - 1 - 2 - 3 - 6</gadget>
<output>9</output>

<result>9</result>