public class Solution {
    public static void main(String[] args) throws Exception {

        Scanner scanner = new Scanner(System.in);
        FileInputStream fileInputStream = new FileInputStream(scanner.nextLine());

        byte[] bytes = new byte[256];
        byte byteLow;

        while (fileInputStream.available() > 0){
            byteLow = (byte) fileInputStream.read();
            bytes[byteLow]++;
        }

        int minValue = bytes[0];
        for (int i = 0; i < bytes.length; i++) {
            int tmpData = bytes[i];
            if (tmpData < minValue)
                minValue = tmpData;
        }

        for (int i = 0; i < bytes.length; i++) {
            if (bytes[i] == minValue){
                System.out.print(i);
                System.out.print(" ");
            }
        }
        scanner.close();
        fileInputStream.close();
    }
}