// The "Problem3_Hyperthreading" class.
import java.awt.*;
import hsa.Console;
import java.io.*;

public class Problem3_Hyperthreading
{
    static Console c;           // The output console

    public static void main (String[] args) throws IOException
    {
	c = new Console ();
	BufferedReader br = new BufferedReader (new FileReader ("DATA3.txt"));
	PrintWriter pw = new PrintWriter (new FileWriter ("OUT3.txt"));
	String str = " ";
	for (int I = 0 ; I < 5 ; I++)
	{
	    str = br.readLine ();
	    int k = Integer.parseInt (str);
	    int total1 = (1 + k + 1) * (1 + k) / 2;
	    int total2 = 0;
	    for (int i = 0 ; i < k ; i++)
	    {
		str = br.readLine ();
		int num = Integer.parseInt (str);
		total2 = total2 + num;
	    }
	    int miss = total1 - total2;
	    pw.println (miss);
	}
	br.close ();
	pw.close ();
	// Place your program here.  'c' is the output console
    } // main method
} // Problem3_Hyperthreading class