题解 | #字符个数统计#

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner fzhinput = new Scanner(System.in);
        String zfc = fzhinput.nextLine();
        int i;
        StringBuilder stack = new StringBuilder();

        Set<Character> unseen = new HashSet<>();

        for(i=0;i<zfc.length();i++){
            char c = zfc.charAt(i);
            if(!unseen.contains(c)){
                stack.append(c);
                unseen.add(c);
            }
        }
        System.out.println(stack.length());
    }
}