Start from A. Each country must begin with the next missing letter in alphabetical order.
Example: Albania -> next required is C. Austria -> next required is B.
Play: Alfafill Hard mode
How to play: The first country must start with A. After each pick, the next country must start with the first letter not yet collected in A-Z order. You can only use each country once.
Remaining letters:26
Highlighted letter on the grid is your required next start.