#include<bits/stdc++.h>
#define int long long
using namespace std;
const int mod = 998244353;
long long qmi(long long a,int b)
{
	long long res = 1;
	while(b)
	{
		if(b & 1) (res *= a) %= mod;
		(a *= a) %= mod;
		b >>= 1;
	}
	return res;
}
int fac[300011],exfac[300011];
int C(int n,int m)
{
	return fac[n] * exfac[m] % mod * exfac[n - m] % mod;
}
int n;
int a[300011];
int siz[300011];
int f[300011];
vector<int> v[300011],e[300011];
void DFS(int p)
{
	siz[p] = 1;
	for(auto i:e[p])
		DFS(i),siz[p] += siz[i];
	int t = siz[p] - 1;
	f[p] = 1;
	for(auto i:e[p])
		f[p] = f[p] * C(t,siz[i]) % mod * f[i] % mod,t -= siz[i];
}
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	cin >> n;
	fac[0] = 1;
	for(int i = 1;i <= n;i++) fac[i] = fac[i - 1] * i % mod;
	exfac[n] = qmi(fac[n],mod - 2);
	for(int i = n;i;i--) exfac[i - 1] = exfac[i] * i % mod;
	for(int i = 1;i <= n;i++)
		cin >> a[i],v[a[i]].push_back(i);
	for(int i = 0;i <= n;i++)
	{
		sort(v[i].begin(),v[i].end(),greater<int>());
		if(v[i].size())
		{
			e[i].push_back(*v[i].begin());
			for(int j = 1;j < v[i].size();j++)
				e[v[i][j - 1]].push_back(v[i][j]);
		}
	}
	DFS(0);
	cout << f[0];
	return 0;
}