There are 13 red balls, 10 yellow balls, and 15 blue balls in the box. How many balls can be drawn from the box to ensure that there are at least 4 balls of all three colors.
箱子里有红球13个，黄球10个，蓝球15个，从中摸出多少个球，才能保证三种颜色的球都至少有4个．
<gadget id="calculator">15 + 13 + 4</gadget>
<output>32</output>

<result>32</result>