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package com.javarush.task.task18.task1804;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
/*
Самые редкие байты
*/
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
FileInputStream inputStream = new FileInputStream(reader.readLine());
int data = 0;
int [] counts = new int[256];
while (inputStream.available() > 0) {
counts[inputStream.read()]++;
}
inputStream.close();
int min = 0;
for (int i = 0; i < counts.length; i++) {
if (counts[i] <= min) {
min = counts[i];
}
}
for (int i = 0; i < counts.length; i++) {
if (counts[i] == min) {
System.out.print(i + " ");
}
}
}
}