If you did not enter expenses in the application, it is possible to use the "Long period without accounting" function, it is in the section "Menu" → "Settings". Swipe down the section "Settings" (more precisely, to the second point below). Enter all data on the quantity of money on accounts at the moment.

The application will count a difference between relevant data which you have just entered and those that were in the application. This difference will be sent to a new account category "Can’t Remember" where all expenses which you did not consider for some time will get.