There are N people, numbered from 0 to N-1, playing a game. The K-th person is assigned the letter S[K]. At the beginning the 0th person sends a message, consisting of a single letter S[0], to the A[0]-th person. When the K-th person receives the message, they append their letter S[K] to the message and forward it to A[K]. The game ends when the 0th person receives the message. Find the final message.