题解 | #字符个数统计#

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);
        String line = in.nextLine();
        char[] chars = line.toCharArray();
        HashSet<Character> set = new HashSet<>();

        for (int i = 0; i < chars.length; i++) {
            set.add(chars[i]);
        }

        System.out.println(set.size());

    }
}