There are 60 wooden blocks of the same size and shape in the black box, and every 15 blocks are painted with the same color. How many blocks can be taken out at a time to ensure that at least 2 wooden blocks have the same color in the period.
黑箱中有60块大小、形状都相同的木块，每15块涂上相同的颜色，一次至少取出多少块才能保证期中至少有2块木块颜色相同．
<gadget id="calculator">60 / 15</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>