package implementation;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class boj5597_과제안내신분 {
public static void main(String[] args) throws IOException{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
ArrayList<Integer> list = new ArrayList<Integer>();
for(int i=1;i<=30;i++)
list.add(i);
int number = 28;
while(number-->0) {
int a = Integer.parseInt(br.readLine());
list.remove(list.indexOf(a));
}
for(int a : list)
System.out.println(a);
}
}