Custom Post auto generate post title incrementally

Hi,
I need help with my custom post. What im trying to achieve is:

1> when a new post is created, the post title should be automatically filled with title and then increment for the next new post added, increment starting from the defined number:

eg:
starting number = 100
first custom post, title should be: “Custom Post# 101”
second custom post title should be: “Custom Post# 102” …
third should be “Custom Post# 103” …and so forth…

How can I go about to achieve this task please

Much appreciated