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();
        String[] arr = str.split("");
        HashSet<String> hashSet = new HashSet<>();
        for(int i = arr.length-1 ; i>=0 ; i--){
            hashSet.add(arr[i]);
        }
        
        System.out.print(hashSet.size());
    }
}