Flagging as 1 n consecutive rows when a condition is met

Assume I have a list that contains either 0 or 1.

Next to this one (call it ColA), I want to add a column (call it ColB) which takes the following values:

i. if ColA == 1, then the next n rows in ColB should be flagged with 1

ii. if ColA == 0, then the corresponding row in ColB should be flagged with 0 unless it is one of those n rows subsequent a 1 in ColA

Can anyone suggest a sketch of code/an idea of how to achieve this?

Any solution in R, SQL, Python or C++ is appreciated.