Track nth row of repeated value in column (R)

Question

I have a dataframe that looks something like this:

test <- data.frame(
  ID = c(1001,1001,1002,1002,1003,1003,1003),
  Complete = c(1, 1, 1, 1, 1, 1,1)
)

I want to create a column that logs the nth row of each ID in consecutive order. The output should look like this:

test <- data.frame(
  ID = c(1001,1001,1002,1002,1003,1003,1003),
  Day = c(1,2,1,2,1,2,3),
  Complete = c(1, 1, 1, 1, 1, 1,1)
)

How can I do this?

Thank you!