#if __has_include("../library/Basic/Debug.hpp")

#include "../library/Basic/Debug.hpp"

#else

/* ----- Header Files ----- */
// IO
#include <cstdio>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm
#include <algorithm>
#include <cmath>
#include <numeric>

// container
#include <vector>
#include <array>
#include <string>
#include <tuple>
#include <complex>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <bitset>

// others
#include <random>
#include <limits>
#include <functional>
#include <ctime>
#include <cassert>
#include <cstdint>

/* ----- Type Alias ----- */
using lint = long long int;
using ldouble = long double;
template <class T>
using MaxHeap = std::priority_queue<T>;
template <class T>
using MinHeap = std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <class T>
T ndvec(T v) { return v; }

template <class T, class... Ts>
auto ndvec(size_t l, Ts... ts) {
    return std::vector<decltype(ndvec<T>(ts...))>(l, ndvec<T>(ts...));
}

template <class Cost = int>
struct Edge {
    int src, dst;
    Cost cost;
    Edge(int src = -1, int dst = -1, Cost cost = 1)
        : src(src), dst(dst), cost(cost){};

    bool operator<(const Edge<Cost>& e) const { return this->cost < e.cost; }
    bool operator>(const Edge<Cost>& e) const { return this->cost > e.cost; }
};

template <class Cost = int>
using Edges = std::vector<Edge<Cost>>;
template <class Cost = int>
using Graph = std::vector<std::vector<Edge<Cost>>>;

#endif

/* ----- Misc ----- */
void fastio() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
}

struct Fout {
    int precision;
    explicit Fout(int precision) : precision(precision) {}
};

std::ostream& operator<<(std::ostream& os, const Fout& fio) {
    os << std::fixed << std::setprecision(fio.precision);
    return os;
}

/* ----- Constants ----- */
// constexpr int INF = std::numeric_limits<int>::max() / 3;
// constexpr int MOD = 1000000007;
// const Real PI = acos(-1);
// constexpr Real EPS = 1e-10;
// std::mt19937 mt(int(std::time(nullptr)));

template <int MOD>
struct ModInt {
    using lint = long long;
    using mint = ModInt<MOD>;

    int val;

    // constructor
    ModInt(lint v = 0) : val(v % MOD) {
        if (val < 0) val += MOD;
    };

    // assignment
    ModInt& operator=(const ModInt& x) {
        if (this != &x) { this->val = x.val; }
        return *this;
    }

    // unary operator
    ModInt operator+() const { return ModInt(val); }
    ModInt operator-() const { return ModInt(MOD - val); }
    ModInt operator~() const {
        // non-recursive extended euclidean algorithm
        int s = val, t = MOD;
        mint sx = 1, sy = 0, tx = 0, ty = 1;
        while (s % t != 0) {
            int div = s / t;
            s -= t * div;
            sx -= tx * div;
            sy -= ty * div;

            std::swap(s, t);
            std::swap(sx, tx);
            std::swap(sy, ty);
        }
        return mint(tx);
    }

    // arithmetic
    ModInt operator+(const ModInt& x) const { return ModInt(*this) += x; }
    ModInt operator-(const ModInt& x) const { return ModInt(*this) -= x; }
    ModInt operator*(const ModInt& x) const { return ModInt(*this) *= x; }
    ModInt operator/(const ModInt& x) const { return ModInt(*this) /= x; }

    // compound assignment
    ModInt& operator+=(const ModInt& x) {
        if ((val += x.val) >= MOD) val -= MOD;
        return *this;
    }
    ModInt& operator-=(const ModInt& x) {
        if ((val -= x.val) < 0) val += MOD;
        return *this;
    }
    ModInt& operator*=(const ModInt& x) {
        val = lint(val) * x.val % MOD;
        return *this;
    }
    ModInt& operator/=(const ModInt& x) { return *this *= ~x; }

    // compare
    bool operator==(const ModInt& b) const { return val == b.val; }
    bool operator!=(const ModInt& b) const { return val != b.val; }

    // I/O
    friend std::ostream& operator<<(std::ostream& os, const ModInt& x) noexcept { return os << x.val; }
};

constexpr int MOD = 998244353;
using mint = ModInt<MOD>;

template <class T, class Int>
T ipow(T b, Int n) {
    T ret = 1;
    while (n > 0) {
        if (n & 1) ret *= b;
        n >>= 1;
        b *= b;
    }
    return ret;
}

void fail() {
    std::cout << 0 << std::endl;
    std::exit(0);
}

int main() {
    int n;
    std::cin >> n;

    int d;
    std::cin >> d;
    if (d != 0) fail();

    std::vector<int> cnt(n - 1, 0);
    for (int v = 1; v < n; ++v) {
        std::cin >> d;
        if (d == 0) fail();
        ++cnt[d - 1];
    }

    while (!cnt.empty() && cnt.back() == 0) {
        cnt.pop_back();
    }

    mint ans = 1;
    int dmax = cnt.size();
    for (int i = 0; i + 1 < dmax; ++i) {
        ans *= ipow(mint(cnt[i]), cnt[i + 1]);
    }

    std::cout << ans << std::endl;
    return 0;
}


Measured memory_bytes: 640