Can someone tell me why doesn't this work?

Question

https://code.sololearn.com/cVSBgih3NW3d/?ref=app

Answer 1

It's because you can't get a digit by index. You either have to make it a string, or use some method to get a digit

Answer 2

annee4 = str(int(annee3[0]) + int(annee3[1]))

annee5 = str(int(annee4[0]) + int(annee4[1]))

Answer 3

This doesn't work either, it tells me string index out of range