A cloth bag contains 10 red, yellow, and green balls of the same size. The number "4" is marked on the red ball, the number "5" is marked on the yellow ball, and the number "5" is marked on the green ball. There are numbers "6". Xiao Ming draws 8 balls from the bag, and the sum of their numbers is 39. Among them, how many balls may be red at most.
一个布袋中装有红、黄、绿三种颜色并且大小相同的小球各10个，红色小球上标有数字"4"，黄色小球上标有数字"5"，绿色小球上标有数字"6"．小明从袋中摸出8个球，它们数字的和是39．其中最多可能有多少个球是红色的．
<result>4</result>