import java.util.Scanner;
 
class Ideone {
	public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        String str = input.nextLine();
        StringBuilder sb = new StringBuilder(str);
 
    	for (int i = sb.length() - 2; i >= 0; i--) {
        	for (int j = i + 1; j < sb.length(); j++) {
            	if (sb.charAt(i) == sb.charAt(j)) {
                	sb.deleteCharAt(j);
                	sb.deleteCharAt(i);
                	break;
            	}
        	}
    	}
 
		System.out.println(sb);
	}
}

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YWFiYWNkYw==

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