Ada and Dishes

Chef Ada is preparing $N$ dishes (numbered $1$ through $N$). For each valid $i$, it takes $C_i$ minutes to prepare the $i$-th dish. The dishes can be prepared in any order. Ada has a kitchen with two identical burners. For each valid $i$, to prepare the $i$-th dish, she puts it on one of the burners and after $C_i$ minutes, removes it from this burner; the dish may not be removed from the burne