p03327 AtCoder Beginner Contest 099 - ABD
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.

Examples

Input

999


Output

ABC


Input

1000


Output

ABD


Input

1481


Output

ABD
```python
print(["ABD","ABC"][len(input())<4])
```