There are 5 balls in each of the 4 colors of red, yellow, blue and green in the pocket. Xiaohua closed his eyes and felt for the balls from his pocket, one ball at a time. How many balls must he draw at least to ensure that there are balls of each color among the balls drawn.
口袋里装有红、黄、蓝、绿4种颜色的球各5个．小华闭着眼睛从口袋里往外摸球，每次摸出1个球．他至少要摸出多少个球才能保证摸出的球中每种颜色的球都有．
<gadget id="calculator">5 + 5 + 5 + 1</gadget>
<output>16</output>

<result>16</result>