Bank system: better to conquer or to defend?

Bank system is having troubles. You are given a collection of K banks. Each bank has a certain amount of money (Mi). A bank i can decide to buy a bank j if its capital Mi is greater than the half of Mj (Mi > Mj/2). When a bank is controlled, its capital can be used by the controller.

A good CEO should decide what strategy to adopt for enlarging its control on other banks, and avoid to be controlled by other banks.

• Can you describe an (heuristic) algorithm for help the CEO?
• Given a solution, can you identify the best CEO (different criteria can be given: who has control on the largest number of banks, who has the largest amount of money, etc)?