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 st = "";
        if(sc.hasNextLine()){
            st = sc.nextLine();
        }
        sc.close();

        char[] chars = st.toCharArray();
        TreeSet<Character> tree = new TreeSet();

        for(int i = 0; i<chars.length; i++){
            tree.add(chars[i]);
        }
        System.out.println(tree.size());
    }
}