CF651A Joysticks

朋友们正要去玩游戏机。他们有两个游戏机，却只有一个充电器。最开始第一个游戏机有a1%的电，第二个游戏机有a2%的电。你只能在每分钟的最开始将一个游戏机接上充电器。每一分钟每个游戏机会消耗2%的电（如果没有接上充电器）或者充上1%的电（如果接上了充电器）。 当两个游戏机都有电时游戏才能继续。因此，如果在某一分钟的开始某个游戏机只有1%的电，它必须接上充电器，否则游戏会停止。如果某个游戏机完全没电（它的电量变为0），游戏也会停下。 试确定该游戏能够持续的最长时间。禁止暂停游戏，即在每一分钟两个游戏机都应该在使用。允许将游戏机充电到超过100%的电量。

输入的第一行包括两个正整数a1、a2（1

输出一个整数，游戏能够持续的最长时间。在某一个游戏机没电之前游戏继续。 感谢@蒟蒻的PSJ 提供的翻译

In the first sample game lasts for 6 minute by using the following algorithm: - at the beginning of the first minute connect first joystick to the charger, by the end of this minute first joystick is at 4%, second is at 3%; - continue the game without changing charger, by the end of the second minute the first joystick is at 5%, second is at 1%; - at the beginning of the third minute connect second joystick to the charger, after this minute the first joystick is at 3%, the second one is at 2%; - continue the game without changing charger, by the end of the fourth minute first joystick is at 1%, second one is at 3%; - at the beginning of the fifth minute connect first joystick to the charger, after this minute the first joystick is at 2%, the second one is at 1%; - at the beginning of the sixth minute connect second joystick to the charger, after this minute the first joystick is at 0%, the second one is at 2%. After that the first joystick is completely discharged and the game is stopped.