public class Solution {
    public char findTheDifference(String s, String t) {
        int book[]=new int[26];
        for(int i=0;i<s.length();i++) book[s.charAt(i)-‘a‘]++;
        for(int i=0;i<t.length();i++) book[t.charAt(i)-‘a‘]--;
        for(int i=0;i<book.length;i++) if(book[i]!=0) return (char)(i+‘a‘);
        return ‘ ‘;
    }
}