#include <cstdio>
#include <cassert>
#include <algorithm>    
#include <iostream>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <iomanip>
#include <cstring>
#include <cmath>
#include <bitset>
#define pb push_back
#define mk make_pair
#define eb emplace_back
#define eps 1e-8
#define fi first
#define se second
#define all(x) (x).begin(),(x).end()
//#define int long long
using namespace std;

typedef long double ld;
typedef unsigned int ui;
typedef pair<int,int> pii;
typedef tuple<int, int, int> tiii;
typedef unsigned long long ull; 
typedef vector<int> vi;
typedef vector<pii> vii;
typedef vector<long double> vd;
const int inf = 1e9;
const long long INF = 1e18;
const int M = 998244353;
//__int128
 
template <int MOD_> struct mod_int {
    static constexpr int MOD = MOD_;
    static_assert(MOD_ > 0, "MOD must be positive");
    int val;
 
    mod_int(long long v = 0) {
        if (v < 0) {
            v = v % MOD + MOD;
        }
 
        if (v >= MOD) {
            v %= MOD;
        }
 
        val = v;
    }
 
    static int mod_inv(int a, int m = MOD) {
        // https://en.wikipedia.org/wiki/Extended_Euclidean_algorithm#Example
        int g = m, r = a, x = 0, y = 1;
 
        while (r != 0) {
            int q = g / r;
            g %= r; swap(g, r);
            x -= q * y; swap(x, y);
        }
 
        return x < 0 ? x + m : x;
    }
 
    explicit operator int() const {
        return val;
    }
 
    mod_int& operator+=(const mod_int &other) {
        val += other.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
 
    mod_int& operator-=(const mod_int &other) {
        val -= other.val;
        if (val < 0) val += MOD;
        return *this;
    }
 
    static unsigned fast_mod(uint64_t x, unsigned m = MOD) {
#if !defined(_WIN32) || defined(_WIN64)
        return x % m;
#endif
        // Optimized mod for Codeforces 32-bit machines.
        // x must be less than 2^32 * m for this to work, so that x / m fits in a 32-bit integer.
        unsigned x_high = x >> 32, x_low = (unsigned) x;
        unsigned quot, rem;
        asm("divl %4\n"
            : "=a" (quot), "=d" (rem)
            : "d" (x_high), "a" (x_low), "r" (m));
        return rem;
    }
 
    mod_int& operator*=(const mod_int &other) {
        val = fast_mod((uint64_t) val * other.val);
        return *this;
    }
 
    mod_int& operator/=(const mod_int &other) {
        return *this *= other.inv();
    }
 
    friend mod_int operator+(const mod_int &a, const mod_int &b) { return mod_int(a) += b; }
    friend mod_int operator-(const mod_int &a, const mod_int &b) { return mod_int(a) -= b; }
    friend mod_int operator*(const mod_int &a, const mod_int &b) { return mod_int(a) *= b; }
    friend mod_int operator/(const mod_int &a, const mod_int &b) { return mod_int(a) /= b; }
 
    mod_int& operator++() {
        val = val == MOD - 1 ? 0 : val + 1;
        return *this;
    }
 
    mod_int& operator--() {
        val = val == 0 ? MOD - 1 : val - 1;
        return *this;
    }
 
    mod_int operator++(int) { mod_int before = *this; ++*this; return before; }
    mod_int operator--(int) { mod_int before = *this; --*this; return before; }
 
    mod_int operator-() const {
        return val == 0 ? 0 : MOD - val;
    }
 
    bool operator==(const mod_int &other) const { return val == other.val; }
    bool operator!=(const mod_int &other) const { return val != other.val; }
 
    mod_int inv() const {
        return mod_inv(val);
    }
 
    mod_int pow(long long p) const {
        assert(p >= 0);
        mod_int a = *this, result = 1;
 
        while (p > 0) {
            if (p & 1)
                result *= a;
 
            a *= a;
            p >>= 1;
        }
 
        return result;
    }
 
    friend ostream& operator<<(ostream &stream, const mod_int &m) {
        return stream << m.val;
    }
    friend istream& operator>>(istream &stream, mod_int &m) {
        return stream >> m.val;
    }
};
 
const int maxn = 2e5;
int c[maxn];

signed main() {
  // freopen("in.txt", "r", stdin);
  ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
  cout.setf(ios::fixed); cout.precision(10);
  int n;
  cin >> n;
  vi a(n);
  for(int i = 0; i < n; ++i) {
    cin >> a[i];
    ++c[a[i]];
  }
  if(a[0] != 0 || c[0] != 1) {
    cout << 0 << endl;
    return 0;
  }
  int tot = 1 + c[1];
  mod_int<M> res = 1, t;
  for(int i = 2; c[i] > 0; ++i) {
    tot += c[i];
    t = c[i - 1];
    // cout << c[i - 1] << ' ' << c[i] << endl;
    res *= t.pow(c[i]);
  }
  if(tot == n) {
    cout << res << endl;
  } else {
    cout << 0 << endl;
  }
  return 0;
}

Measured memory_bytes: 1024