#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  constexpr int A = 100000;
  int n; cin >> n;
  int nums[A + 1]{}, rem = n;
  while (n--) {
    int a; cin >> a;
    ++nums[a];
  }
  REP(i, A + 1) {
    if (nums[i] == 0) {
      cout << i << '\n';
      return 0;
    }
    rem -= nums[i];
    if (nums[i] == 1) {
      if (rem > 0) {
        for (int j = i + 1; ; ++j) {
          if (nums[j] < 2) {
            cout << j << '\n';
            break;
          }
        }
      } else {
        cout << i << '\n';
      }
      return 0;
    }
    rem += nums[i] - 2;
  }
  assert(false);
}