题解 | #字符个数统计#

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        Set<Character> set = new HashSet<>();
        int count = 0;
        for (int i = 0; i < str.length(); i++) {
            if (set.add(str.charAt(i))) {
                count++;
            }
        }
        System.out.println(count);
    }
}