Competitions
SEERC 2021
Reverse Game
Alice and Bob are playing a turn-based game. The rules of the game are as follows:
- At the beginning of the game some binary string s is chosen.
- On his turn player has to choose some substring t of s, equal to one of 10, 110, 100, 1010. Then the player has to reverse t. For example, if s = 010101, the player can select substring t = 1010 and reverse it, obtaining s = 001011.
- The player who can’t make a move (who can’t choose an appropriate substring t) loses.
- The players cannot skip a turn.
Which player has the winning strategy, if Alice moves first?
A string a is a substring of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters from the beginning and several (possibly, zero or all) characters from the end.
Input
The only line contains a binary string s (1 ≤ |s| ≤ 106
) - the string with which Alice and Bob play.
Output
If Alice wins, output Alice. Otherwise, output Bob.
Note
In the first sample, Alice can choose substring 10 of 010 and reverse it, obtaining string 001. Bob can’t make any move with this string, and loses.
In the second sample, Alice can’t make a single move and loses.
Input example #1
010
Output example #1
Alice
Input example #2
1111
Output example #2
Bob
Input example #3
1010
Output example #3
Bob
Input example #4
1010001011001
Output example #4
Alice