Counting/repeating with conditions R

From a question I asked before (Count with conditions in R dataframe), I have the following table:

  Week   SKU   Discount(%)   Duration  LastDiscount
     1     111       5            2           0
     2     111       5            2           0
     3     111       0            0           0
     4     111      10            2           0
     5     111      11            2           2
     1     222       0            0           0
     2     222      10            3           0
     3     222      15            3           0
     4     222      20            3           0

I want the LastDiscount count to be in the first row where there is a different discount for the same SKU in different weeks. For example, the SKU 111 had a discount in the 2nd week and the next discount is in the 4th week, that gives 2 weeks since the last discount but the problem is that I want the result to be in the 4th week where starts the next discount campaign.

Something like this:

  Week   SKU   Discount(%)   Duration  LastDiscount
     1     111       5            2           0
     2     111       5            2           0
     3     111       0            0           0
     4     111      10            2           2
     5     111      11            2           0
     1     222       0            0           0
     2     222      10            3           0
     3     222      15            3           0
     4     222      20            3           0

I have this code right now:

df1 %>%
  group_by(SKU) %>% 
  mutate(Duration = with(rle(Discount > 0), rep(lengths*values, 
        lengths)),
         temp = with(rle(Discount > 0), sum(values != 0)), 
         LastDiscount = if(temp[1] > 1) c(rep(0, n()-1), temp[1]) else 0) %>%
  select(-temp)