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());

        TreeSet<Integer> set = new TreeSet<>();

        while (inputStream.available() > 0){
            set.add(inputStream.read());
        }

        System.out.println(set.first());
        inputStream.close();
    }
}