Split Stones

There are three piles of stones. The first pile contains $a$ stones, the second pile contains $b$ stones and the third pile contains $c$ stones. You must choose one of the piles and split the stones from it to the other two piles; specifically, if the chosen pile initially contained $s$ stones, you should choose an integer $k$ ($0 \le k \le s$), move $k$ stones from the chosen pile onto one of the