#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef int64_t lint;
#define rep(i, n) for(int i=0; i<n; i++)
#define repx(i, l, n) for(int i=l; i<n; i++)
#define all(v) v.begin(), v.end()
#define show(x) cout << #x << ": " << x << endl;
#define list(x) cout << #x << ": " << x << "  ";
#define pb push_back
using vi = vector<lint>;
using vvi = vector<vector<lint>>;
template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> inline void drop(T x) { cout << x << endl; exit(0); }
template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; }
constexpr lint LINF = LLONG_MAX/2;
using mint = modint998244353;
using vm = vector<mint>;

int main() {
	lint N;
	cin >> N;
	vi v(N), w(N);
	vin(v);

	lint a=0, b=0, c=0, x, y, z;
	w[0] = v[0]; w[N-1] = v[N-1];
	set<lint> s;
	s.insert(v[0]);
	s.insert(v[N-1]);
	repx(i, 1, (N+1)/2) {
		w[i] = w[i-1];
		w[N-1-i] = w[N-i];
		if (chmin(w[i], v[i])) s.insert(v[i]);
		if (chmin(w[N-1-i], v[N-1-i])) s.insert(v[N-1-i]);
	}
	w.pb(LINF);
	reverse(all(w));
	w.pb(LINF);
	reverse(all(w));
	a = (N-1)/2+1;
	b = N/2+1;
	mint ans = 1;
	rep(i, N) {
		if (s.count(i)) continue;
		while(w[a] < i) a--;
		while(w[b] < i) b++;
		ans *= b-a-1-i;
	}
	std::cout << ans.val() << '\n';
}