Summing numbers only if they correspond to another column???

Been working on this forever so I decided to join this forum to try to find out. There has to be a better way on this.
I added an attachment. Column A is my "week number" and column E is my sales amount.

I'm trying to create a formula that sums the sales amount, only if it corresponds to a certain week number. I know sumif formulas, but can't get them to work well for this. For example, I want it to sum all the sale that happened in week one, then all the ones in week 2, then all the ones in week 3, and so on. There has to be an easier way than doing a sumif for each individual week and manually changing the week number in the sum if formula.

Could there be a character you can use in a formula to make the sumif week number "running?" So you could then just type in the formula once and pull it all the way down for the year, so the formula will work for the every week throughout the year? Thanks so much for helping.