Related: 100299K - Digraphs, 290508668

The first case in test 3 was (like the following one):

676
aa
ab
ac
...

And my output for the case was (ASCII 96):

`

That was an illegal character, yet the checker gave me an accepted???

It's been 10 (11?) years yet I'm the first one who discover this...

MikeMirzayanov fix this please...