#define _USE_MATH_DEFINES #include 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 inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; } template 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); }