// need
#include <iostream>
#include <algorithm>
// data structure
#include <bitset>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#include <complex>
//#include <deque>
#include <valarray>
#include <unordered_map>
#include <array>
// stream
//#include <istream>
//#include <sstream>
//#include <ostream>
#include <fstream>
// etc
#include <cassert>
#include <cmath>
#include <functional>
#include <iomanip>
//#include <chrono>
#include <random>
#include <numeric>

// input
#define INIT std::ios::sync_with_stdio(false);std::cin.tie(0);
#define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__);
template<typename T> void MACRO_VAR_Scan(T& t) { std::cin >> t; }
template<typename First, typename...Rest>void MACRO_VAR_Scan(First& first, Rest&...rest) { std::cin >> first; MACRO_VAR_Scan(rest...); }
#define VEC_ROW(type, n, ...)std::vector<type> __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int w=0; w<n; ++w){MACRO_VEC_ROW_Scan(w, __VA_ARGS__);}
template<typename T> void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); }
template<typename First, typename...Rest>void MACRO_VEC_ROW_Init(int n, First& first, Rest&...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); }
template<typename T> void MACRO_VEC_ROW_Scan(int p, T& t) { std::cin >> t[p]; }
template<typename First, typename...Rest>void MACRO_VEC_ROW_Scan(int p, First& first, Rest&...rest) { std::cin >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); }
#define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
#define MAT(type, c, m, n) std::vector<std::vector<type>> c(m, std::vector<type>(n));for(auto& R:c)for(auto& w:R)std::cin>>w;
// output
#define OUT(dist) std::cout<<(dist);
#define FOUT(n, dist) std::cout<<std::fixed<<std::setprecision(n)<<(dist);
#define SOUT(n, c, dist) std::cout<<std::setw(n)<<std::setfill(c)<<(dist);
#define SP std::cout<<" ";
#define TAB std::cout<<"\t";
#define BR std::cout<<"\n";
#define SPBR(w, n) std::cout<<(w + 1 == n ? '\n' : ' ');
#define ENDL std::cout<<std::endl;
#define FLUSH std::cout<<std::flush;
#define SHOW(dist) {std::cerr << #dist << "\t:" << (dist) << "\n";}
#define SHOWVECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
#define SHOWVECTOR2(v) {std::cerr << #v << "\t:\n";for(const auto& xxx : v){for(const auto& yyy : xxx){std::cerr << yyy << " ";}std::cerr << "\n";}}
#define SHOWQUEUE(a) {auto tmp(a);std::cerr << #a << "\t:";while(!tmp.empty()){std::cerr << tmp.front() << " ";tmp.pop();}std::cerr << "\n";}
// utility
#define ALL(a) (a).begin(),(a).end()
#define FOR(w, a, n) for(int w=(a);w<(n);++w)
#define RFOR(w, a, n) for(int w=(n)-1;w>=(a);--w)
#define REP(w, n) for(int w=0;w<int(n);++w)
#define RREP(w, n) for(int w=int(n)-1;w>=0;--w)
#define FORLL(w, a, n) for(ll w=ll(a);w<ll(n);++w)
#define RFORLL(w, a, n) for(ll w=ll(n)-1;w>=ll(a);--w)
#define REPLL(w, n) for(ll w=0;w<ll(n);++w)
#define RREPLL(w, n) for(ll w=ll(n)-1;w>=0;--w)
#define IN(a, x, b) (a<=x && x<b)
template<class T> inline T CHMAX(T& a, const T b) { return a = (a < b) ? b : a; }
template<class T> inline T CHMIN(T& a, const T b) { return a = (a > b) ? b : a; }
#define EXCEPTION(msg) throw std::string("Exception : " msg " [ in ") + __func__ + " : " + std::to_string(__LINE__) + " lines ]"
#define TRY(cond, msg) try {if (cond) EXCEPTION(msg);}catch (std::string s) {std::cerr << s << std::endl;}
//void CHECKTIME(std::function<void()> f) { auto start = std::chrono::system_clock::now(); f(); auto end = std::chrono::system_clock::now(); auto res = std::chrono::duration_cast<std::chrono::nanoseconds>((end - start)).count(); std::cerr << "[Time:" << res << "ns  (" << res / (1.0e9) << "s)]\n"; }
// test
template<class T> std::vector<std::vector<T>> VV(int n, int m, T init = T()) {
	return std::vector<std::vector<T>>(n, std::vector<T>(m, init));
}
template<typename S, typename T>
std::ostream& operator<<(std::ostream& os, std::pair<S, T> p) {
	os << "(" << p.first << ", " << p.second << ")"; return os;
}

// type/const
#define int ll
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using PAIR = std::pair<int, int>;
using PAIRLL = std::pair<ll, ll>;
constexpr int INFINT = 1 << 30;                          // 1.07x10^ 9
constexpr int INFINT_LIM = (1LL << 31) - 1;              // 2.15x10^ 9
constexpr ll INFLL = 1LL << 60;                          // 1.15x10^18
constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62);  // 9.22x10^18
constexpr double EPS = 1e-10;
constexpr int MOD = 998244353;
constexpr double PI = 3.141592653589793238462643383279;
template<class T, size_t N> void FILL(T(&a)[N], const T& val) { for (auto& x : a) x = val; }
template<class ARY, size_t N, size_t M, class T> void FILL(ARY(&a)[N][M], const T& val) { for (auto& b : a) FILL(b, val); }
template<class T> void FILL(std::vector<T>& a, const T& val) { for (auto& x : a) x = val; }
template<class ARY, class T> void FILL(std::vector<std::vector<ARY>>& a, const T& val) { for (auto& b : a) FILL(b, val); }
// ------------>8------------------------------------->8------------

// Description: 区間をsetで管理するデータ構造(なお実装はmap)．各クエリO(log区間数)．

// #### attention! : [l, r] ( include r, not [l, r) )
class SegmentMap : public std::map<signed, signed> {
private:
	bool flagToMergeAdjacentSegment;
public:
	// if merge [l, c] and [c+1, r], set flagToMergeAdjacentSegment to true
	SegmentMap(bool flagToMergeAdjacentSegment) :
		flagToMergeAdjacentSegment(flagToMergeAdjacentSegment) {}
	// __exist -> iterator pair(l, r) (contain p)
	// noexist -> map.end()
	auto get(signed p) const {
		auto it = upper_bound(p);
		if (it == begin() || (--it)->second < p) return end();
		return it;
	}
	// insert segment [l, r]
	void insert(signed l, signed r) {
		auto itl = upper_bound(l), itr = upper_bound(r + flagToMergeAdjacentSegment);
		if (itl != begin()) {
			if ((--itl)->second < l - flagToMergeAdjacentSegment) ++itl;
		}
		if (itl != itr) {
			l = std::min(l, itl->first);
			r = std::max(r, std::prev(itr)->second);
			erase(itl, itr);
		}
		(*this)[l] = r;
	}
	// remove segment [l, r]
	void remove(signed l, signed r) {
		auto itl = upper_bound(l), itr = upper_bound(r);
		if (itl != begin()) {
			if ((--itl)->second < l) ++itl;
		}
		if (itl == itr) return;
		int tl = std::min(l, itl->first), tr = std::max(r, std::prev(itr)->second);
		erase(itl, itr);
		if (tl < l) (*this)[tl] = l - 1;
		if (r < tr) (*this)[r + 1] = tr;
	}
	// Is p and q in same segment?
	bool same(signed p, signed q) const {
		const auto&& it = get(p);
		return it != end() && it->first <= q && q <= it->second;
	}
};

int n;
PAIR getSeg(const std::vector<int>& a) {
	if (a.empty()) return PAIR(-1, -1);
	if (a.size() == 1) return PAIR(a[0], a[0]);
	int k = a.size();
	std::vector<int> b;
	if (a.front() == 0) {
		if (a.back() != n - 1) b.emplace_back(0);
	}
	else {
		b.emplace_back(0);
	}
	REP(i, k - 1) if (a[i] + 1 != a[i + 1]) b.emplace_back(i + 1);
	if (b.size() == 0) return PAIR(n, n);
	if (b.size() >= 2) return PAIR(-1, -1);
	int last = (b[0] == 0) ? a.back() : a[b[0] - 1];
	return PAIR(a[b[0]], last);
}

signed main() {
	INIT;

	VAR(int, n_); n = n_;
	VEC(int, a, n);
	REP(i, n) --a[i];
	{
		std::vector<int> a0;
		REP(i, n) {
			if (a[i] == 0) a0.emplace_back(i);
		}
		PAIR p0(getSeg(a0));
		if (p0.first == n) {
			int ans = 1;
			REP(i, n) (ans *= i + 1) %= MOD;
			OUT(ans)BR;
			return 0;
		}
		if (p0.first == -1) {
			OUT(0)BR;
			return 0;
		}
		if (p0.first != 0) {
			std::rotate(a.begin(), a.begin() + p0.first, a.end());
		}
	}

	std::vector<std::vector<int>> num(n);
	REP(i, n) num[a[i]].emplace_back(i);

	PAIR p0 = getSeg(num[0]);

	SegmentMap sm(true);

	int cnt = num[0].size();
	for (auto& p : num[0]) sm.insert(p, p);

	int rest = 0;
	int ans = 1;
	FOR(x, 1, n) {
		if (num[x].size()) {
			auto pa(getSeg(num[x]));
			if (pa.first == -1) {
				OUT(0)BR;
				return 0;
			}
			if (num[x].size() <= cnt) {
				int add = 0;
				bool cntadd = 0;
				bool existL = false, existR = false;
				{
					int t = pa.first - 1;
					auto it = sm.get(t);
					if (it != sm.end()) add += (int)num[x].size() - 1, ++cntadd, existL = true;
				}
				{
					int t = pa.second + 1;
					auto it = sm.get(t);
					if (t >= n || it != sm.end()) add += (int)num[x].size() - 1, ++cntadd, existR = true;
				}
				if (cntadd == 2) {
					add = cnt + (int)num[x].size() - 2;
				}
				rest += add;

				sm.insert(pa.first, pa.second);
				auto it = sm.get(pa.first);

				int L = it->first, R = it->second;
				if (L == 0) {
					auto it2 = sm.get(n - 1);
					if (it2 != sm.end()) L = it2->first;
				}
				if (R == n - 1) {
					auto it2 = sm.get(0);
					if (it2 != sm.end()) R = it2->second;
				}

				if (L == pa.first && R == pa.second && (int)num[x].size() < cnt) {
					ans = 0;
					break;
				}

				int coef = 0;
				if (L == 0 && R == n - 1) {
					coef = cnt - (int)num[x].size() + 1;
					rest = n - x - 1;
				}
				else {
					int l = pa.second - cnt + 1;
					if (!existL) l = pa.first;
					int r = pa.first;
					if (!existR) r = pa.second - cnt + 1;
					coef = r - l + 1;
					if (coef < 0) coef = 0;
				}
				(ans *= coef) %= MOD;
			}
			else if (num[x].size() > cnt) {
				OUT(0)BR;
				return 0;
			}
		}
		else {
			(ans *= rest) %= MOD;
			--rest;
		}

		for (auto& p : num[x]) sm.insert(p, p);
	}
	OUT(ans)BR;
	assert(ans >= 0);
	return 0;
}

/*
1の区間を見定める
2以上の数xについて:
	aにxがあるとき，その区間を見定めてどこかと重なっていたら余裕度合いに重なり分-1を加える
	aにxがないとき，余裕度合いを答えに掛け算して余裕度合いを-1する

*/