import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Scanner; //制造回文 public class MakePlalindrome { public static void main(String[] args) { int result = 0; Map<Character, Integer> dic = new HashMap<Character, Integer>(); Scanner input = new Scanner(System.in); String str = input.nextLine(); char[] chars = str.toCharArray(); for (char c : chars) { if(!dic.containsKey(c)){ dic.put(c, 1); }else{ dic.put(c, dic.get(c)+1); } } // System.out.println(dic.toString()); Iterator iter = dic.entrySet().iterator(); while (iter.hasNext()) { Map.Entry entry = (Map.Entry) iter.next(); int val = (int) entry.getValue(); if(val%2 == 1){ result++; } } System.out.println(result); } }