题解 | #字符个数统计#

import java.util.Scanner;
import java.util.HashSet;
// 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 input = new Scanner(System.in);
        String next = input.next();
        StringBuilder stringBuilder = new StringBuilder(next);
        HashSet<Character> set = new HashSet<>();
        for (int i = 0; i < stringBuilder.length();i++) {
            set.add(stringBuilder.charAt(i));
        }
        System.out.println(set.size());
    }
}