有一个盒子，混装了数量相等的围棋白子和黑子。现在要用自动分拣系统把白子和黑子分开。设系统有两个进程P1和P2，其中P1拣白子，P2拣黑子。当一个进程在拣子时，不允许另一进程去拣。试写出这两个并发进程能正确执行的程序。-There is a box, mixed up an equal number of Go albino and sunspots. Now use the automatic sorting system to separate the white out and sunspots. Suppose there are two processes P1 and P2, where P1 pick albino, P2 pick sunspots. When a process in picking midnight, do not allow another process Qujian. Write down the two concurrent processes that execute the procedure correctly.