#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  constexpr int n = 9;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  rep(i, 10) {
    bool exist = false;
    rep(j, n) {
      if (a[j] == i + 1) {
        exist = true;
        break;
      }
    }
    if (!exist) {
      cout << i + 1 << endl;
      return 0;
    }
  }
  return 0;
}