Phoenix and Skipping Stones

Today is a very special day for Phoenix as there is a large fair in his city and so he goes in. He finds a game quite amusing and enters it, only to find that he isn’t able to exit it without completing the game. The game has the following rules : There are $N$ number of stones and each stone has $26$ different possibilities of being painted with any letter from $a$ to $z$. Now, Phoenix can s