Help to understand

Question

please help fill the blank
https://code.sololearn.com/czN00778TECV/?ref=app

Answer 1

return A[0]+addlist(A[1:])... Here is how the whole function works:
If the list has length 1, it just returns the item in the list
Otherwise it returns the item in position 0 + what will be return when we add the remaining items in the list ( meaning A[0] + addlist(A[1:]) )