Three-Generation Chain

A "grandparent" process forks to create a "parent" process. That parent, in turn, forks to create a "grandchild". Each generation prints its level and its own PID, but printing goes from grandchild up to grandparent: every parent uses wait(NULL) to let its own child finish before printing.

The structure looks like fork inside fork: after the first fork(), the child calls fork() again. Watch the return 0 placement: if it's missing, the "wrong" processes continue running the code below.

Input

• No input.

Output

• 3 lines, in reverse generation order:
  • Level 2 (grandchild): PID X
  • Level 1 (parent): PID Y
  • Level 0 (grandparent): PID Z

PIDs differ on every run, but the order of the lines is always grandchild → parent → grandparent.

Example

Output:
Level 2 (grandchild): PID 45
Level 1 (parent): PID 44
Level 0 (grandparent): PID 43

Use fork(), getpid() and wait(NULL).