#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "math.h"
#include "utility"
#include "map"

using namespace std;
const long long int MOD = 1000000007;

int N;
bool flag[11];

int main() {
	for (int i = 0; i < 9; i++) {
		cin >> N;
		flag[N] = true;
	}
	for (int i = 1; i <= 10; i++) {
		if (!flag[i])cout << i << endl;
	}
	return 0;
}