#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <fstream>
#include <set>
#include <utility>
#include <algorithm>

using namespace std;

int max(int x, int y) {
	int a;
	(x > y) ? a = x : a = y;
	return a;
}

int min(int x, int y) {
	int a;
	(x < y) ? a = x : a = y;
	return a;
}

int main() {
	int x[11];
	for (int i = 0; i < 11; i++) x[i] = 1;

	int n;
	for (int i = 0; i < 9; i++) {
		cin >> n;
		x[n] = 0;
	}

	for (int i = 1; i < 11; i++)if (x[i])cout << i << endl;

	return 0;
}