Decades have passed since the beginning of AtCoder Beginner Contest.
The contests are labeled as ABC001, ABC002, ... from the first round, but after the 999-th round ABC999, a problem occurred: how the future rounds should be labeled?
In the end, the labels for the rounds from the 1000-th to the 1998-th are decided: ABD001, ABD002, ..., ABD999.
You are given an integer N between 1 and 1998 (inclusive). Print the first three characters of the label of the N-th round of AtCoder Beginner Contest.

-----Constraints-----
- $1 \leq N \leq 1998$
- N is an integer.

-----Input-----
Input is given from Standard Input in the following format:
N

-----Output-----
Print the first three characters of the label of the N-th round of AtCoder Beginner Contest.

-----Sample Input-----
999

-----Sample Output-----
ABC

The 999-th round of AtCoder Beginner Contest is labeled as ABC999.

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