TSTST 2020 Problem 1

Let $a, b, c$ be fixed positive integers. There are $a+b+c$ ducks sitting in a circle, one behind the other. Each duck picks either rock, paper, or scissors, with $a$ ducks picking rock, $b$ ducks picking paper, and $c$ ducks picking scissors. A move consists of an operation of one of the following three forms: - If a duck picking rock sits behind a duck picking scissors, they switch places. - If a duck picking paper sits behind a duck picking rock, they switch places. - If a duck picking scissors sits behind a duck picking paper, they switch places. Determine, in terms of $a, b$, and $c$, the maximum number of moves which could take place, over all possible initial configurations.