There are 3 balls of red, green and yellow in the drawer. How many can be drawn at least once to ensure that there is at least one of each color?
抽屉里放着红、绿、黄三种颜色的球各3只．一次至少摸出多少只才能保证每种颜色至少有一只？
<gadget id="calculator">3 + 3 + 1</gadget>
<output>7</output>

<result>7</result>