enter the number of levels
[1] pid 1568 ppid 1567
[1] pid 1637 ppid 1568 created left child
[3] pid 1637 ppid 1568
[1] pid 1636 ppid 1568 created right child
[4] pid 1636 ppid 1568
[2] pid 1639 ppid 1637 created left child
[5] pid 1639 ppid 1637
[3] -1 left child of pid 1637 with exit status 10
[3] -1 right child of pid 1637 with exit status 9
[2] pid 1638 ppid 1637 created right child
[6] pid 1638 ppid 1637
[4] -1 left child of pid 1637 with exit status 13
[4] -1 right child of pid 1637 with exit status 12
[2] 1638 left child of pid 1568 with exit status 5
[2] 1639 right child of pid 1568 with exit status 4
[3] pid 1641 ppid 1636 created left child
[6] pid 1641 ppid 1636
[4] -1 left child of pid 1636 with exit status 13
[4] -1 right child of pid 1636 with exit status 12
[3] pid 1640 ppid 1636 created right child
[7] pid 1640 ppid 1636
[5] -1 left child of pid 1636 with exit status 16
[5] -1 right child of pid 1636 with exit status 15
[3] 1640 left child of pid 1568 with exit status 7
[3] 1641 right child of pid 1568 with exit status 6
[1] 1636 left child of pid 1567 with exit status 3
[1] 1637 right child of pid 1567 with exit status 2