#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream> 
#include<map>
#include <iomanip>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
using namespace std;
#define MAX_MOD 1000000007
#define REP(i,n) for(long long i = 0;i < n;++i)
#define LONG_INF 800000000000000000
int main() {
	vector<int> b;
	REP(i, 9) {
		int tmp;
		cin >> tmp;
		b.push_back(tmp);
	}
	sort(b.begin(), b.end());
	for (int i = 0;i < 9;++i) {
		if (b[i] != i + 1) {
			cout << i + 1 << endl;
			return 0;
		}
	}
	cout << 10 << endl;
}