There are four balls of different colors in a pocket. Each time you touch 2 pieces, you must ensure that the result of 10 touches is the same, at least how many times you need to touch.
一个口袋里有四种不同颜色的小球．每次摸出2个，要保证有10次所摸的结果是一样的，至少要摸多少次．
<gadget id="calculator">9 * 10</gadget>
<output>90</output>

<gadget id="calculator">90 + 1</gadget>
<output>91</output>

<result>91</result>