I have noticed that educational rounds like to use mod 998244353 instead of mod 10⁹ + 7. Does anyone know the reason for this? One idea that comes to mind is since 998244353 < 10⁹ there might be opportunities to troll contestants by breaking division and forcing them to calculate things like mod 998244353. However I have yet to see this used in an educational round, although this idea was used to good effect in 272D - Dima and Two Sequences.