删除字符串中出现次数最少的字符

mport java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;


public class Main
{

     public static void main(String[] args)
     {//abcdabcddd
          StringBuilder res = new StringBuilder(256);
          Scanner sc =new Scanner(System.in);
          String input = sc.nextLine();
         
          if(input.length() > 20) return ;
          HashMap<Character, Integer> map = new HashMap<Character, Integer>();
          //count character times
          char[] chs = input.toCharArray();
          for(char ch : chs)
          {
               if(!map.containsKey(ch))
               {
                    map.put(ch,1);
               }
               else
               {
                    map.put(ch,map.get(ch)+1);
               }
          }
         
          int min = Collections.min(map.values());
          //delete
          for(char ch :chs)
          {
               if(min != map.get(ch))
                    res.append(ch);
          }
         

          System.out.println(res.toString());   
         
     }

}