package me.yukicoder.lv1;

import java.util.Scanner;

public class No0481 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int sum = 10 * (10 + 1) / 2;// 1から10までの合計
		int num = sc.nextInt();// 書いた数9個の合計

		while (sc.hasNext()) {
			num += sc.nextInt();
		}

		System.out.println(sum - num);
	}
}