Divide into 3

You have $N$ toffees and $3$ friends. You will divide the toffees among your friends (You are too generous to take one yourself). You want to make sure that your division is fair. Hence, you want to minimize the *imbalance* of your division. Here, the imbalance is defined as $(\text{mx} - \text{mn})$, where $\text{mx}$ is the maximum toffees any friend received, and $\text{mn}$ is the minimum t