import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.stream.IntStream;

public class No0481 {
	public static void main(String[] args) {
		try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
			String[] strArray = br.readLine().trim().split(" ");
			int sum = IntStream.rangeClosed(1, 10).sum();
			int num = 0;//書いた数9個の合計

			for (String s : strArray) {
				num += Integer.parseInt(s);
			}

			System.out.println(sum - num);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}