NEERC Subregional problems

[Artikali]

Problems:
http://neerc.ifmo.ru/subregions/northern/problems.pdf

and official test cases:
http://neerc.ifmo.ru/subregions/northern/tests.rar
in this file also has check.exe which is check your answer

after the constest i soved all problem, which i couldn't solved during the contest, except one.

First problem Alphabet, could any one will try two solve this one.
if you solve, please share me your algo.

thanks.

[Artikali]

problem Alphabet, have anyone interested with this problem, i think it is a np-complete.