There are 51 identically numbered balls in a pocket, among which there are 3, 6, 10, 12, and 20 balls numbered 1, 2, 3, 4, and 5 respectively. Randomly take the ball from the pocket, at least how many small balls must be taken out to ensure that there are at least 7 small balls with the same number.
一个口袋中有51个编上号码的相同的小球，其中编号为1，2，3，4，5的小球分别有3，6，10，12，20个．任意从口袋中取球，至少要取出多少个小球，才能保证其中至少有7个号码相同的小球．
<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">3 + 24 + 1</gadget>
<output>28</output>

<result>28</result>