Score : $100$ points

问题描述

自 AtCoder Beginner Contest 开始以来，已经过去了数十年。

这些比赛按照从第一轮开始的顺序被标记为 ABC001、ABC002、$...$ 等，但在第 $999$ 轮 ABC999 后，出现了一个问题：后续的比赛应该如何进行标记？

最终，决定从第 $1000$ 轮到第 $1998$ 轮的比赛标签为：ABD001、ABD002、$...$、ABD999。

给你一个整数 $N$，范围在 $1$ 到 $1998$（包含两端点）。请你输出第 $N$ 轮 AtCoder Beginner Contest 的标签的前三个字符。

以上为通义千问 qwen-max 翻译，仅供参考。

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.

update @ 2024/3/10 17:18:45