#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll inf=1444999994999999;
ll mod=998244353;
int main(){
    ll n;
    cin >> n;
    vector<ll>p(n);
    ll left=inf,right=0;
    vector<ll>memo(n);
    for (ll i = 0; i < n; i++)
    {
        cin >> p[i];
        memo[p[i]]=i;
        if (p[i]==0||p[i]==1)
        {
            left=min(left,i);
            right=max(right,i);
        }
    }
    ll ans=1;
    for (ll i = 2; i < n; i++)
    {
        if (left<=memo[i]&&memo[i]<=right)
        {
            ans*=(right-left-i+1);
            ans%=mod;
        }
        left=min(left,memo[i]);
        right=max(memo[i],right);
    }
    cout << ans << endl;
}