#include <bits/stdc++.h>
#include <vector>
#include <iostream>
#include <map>
#include <string>
#include <cmath>
#include <algorithm>
#include <queue>
#include <math.h>
#include <ctype.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repe(i,x,n) for(int i=x; i<(n); ++i)
using ll = long long;
using P = pair<int, int>;
#define pai 3.1415926535897932384
#define INF 10010010000
#define _GLIBCXX_DEBUG
#define All(a) (a).begin(),(a).end()
#define rAll(a) (a).rbegin(),(a).rend()
#define pb push_back
#define mk make_pair
#define yes cout << "Yes" << endl;
#define no cout << "No" << endl;
#define mod 998244353
#define mod2 1000000007
#define deci cout << fixed << setprecision(10);
#define nextP next_permutation
#define em emplace_back

int main() {

    set<int> s;
    for(int i=0; i<9; i++) {
        int num;
        cin >> num;
        s.insert(num);
    }
    for(int i=1; i<=10; i++) {
        if(!s.count(i)) {
            cout << i << endl;
            return 0;
        }
    }

}