Problem Statement

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 1

999

Sample Output 1

ABC

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

Sample Input 2

1000

Sample Output 2

ABD

The $1000$-th round of AtCoder Beginner Contest is labeled as ABD001.

Sample Input 3

1481

Sample Output 3

ABD

The $1481$-th round of AtCoder Beginner Contest is labeled as ABD482.