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 str = in.nextLine();
        char[] array = str.toCharArray();

        HashSet<Character> set = new HashSet<>();
        for (int i = 0; i < array.length; i++) {
            set.add(array[i]);
        }

        System.out.print(set.size());
    }

}