Just Move Them

Logic

There are 3 boxes $A$ , $B$ , and $C$ . Initially, box $A$ has 8 balls but $B$ and $C$ are empty. Chris wants box $C$ to have as many balls as possible. He can do so by moving some balls from a box to another with the constraint that he can only move exactly $i$ balls on the $i^{\text{th}}$ step.

What is the maximum possible number of balls box $C$ can have?