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 (or 11) years yet nobody have discovered this before...
MikeMirzayanov fix this please...