Packing Balls

You have $R$ red balls, $G$ green balls, and $B$ blue balls.

Pack all of them into boxes. One box holds 1, 2, or 3 balls.

The balls inside a single box must be all the same color or all different colors.

Write a program that finds the minimum number of boxes needed to pack every ball.

The first line contains $R$, $G$, and $B$, separated by spaces. ($1 \le R, G, B \le 100$)

Print the minimum number of boxes on the first line.

The first example can be packed as (red, green, blue), (red, green), (red, red), (blue, blue, blue).

The second example is packed as (red, green, blue), (green, green, green), (green, green, green).