#include <bits/stdc++.h>
using namespace std;

template <int MOD_> struct modnum {
	static constexpr int MOD = MOD_;
	static_assert(MOD_ > 0, "MOD must be positive");

private:
	using ll = long long;

	int v;

	static int minv(int a, int m) {
		a %= m;
		assert(a);
		return a == 1 ? 1 : int(m - ll(minv(m, a)) * ll(m) / a);
	}

public:

	modnum() : v(0) {}
	modnum(ll v_) : v(int(v_ % MOD)) { if (v < 0) v += MOD; }
	explicit operator int() const { return v; }
	friend std::ostream& operator << (std::ostream& out, const modnum& n) { return out << int(n); }
	friend std::istream& operator >> (std::istream& in, modnum& n) { ll v_; in >> v_; n = modnum(v_); return in; }

	friend bool operator == (const modnum& a, const modnum& b) { return a.v == b.v; }
	friend bool operator != (const modnum& a, const modnum& b) { return a.v != b.v; }

	modnum inv() const {
		modnum res;
		res.v = minv(v, MOD);
		return res;
	}
	friend modnum inv(const modnum& m) { return m.inv(); }
	modnum neg() const {
		modnum res;
		res.v = v ? MOD-v : 0;
		return res;
	}
	friend modnum neg(const modnum& m) { return m.neg(); }

	modnum operator- () const {
		return neg();
	}
	modnum operator+ () const {
		return modnum(*this);
	}

	modnum& operator ++ () {
		v ++;
		if (v == MOD) v = 0;
		return *this;
	}
	modnum& operator -- () {
		if (v == 0) v = MOD;
		v --;
		return *this;
	}
	modnum& operator += (const modnum& o) {
		v += o.v;
		if (v >= MOD) v -= MOD;
		return *this;
	}
	modnum& operator -= (const modnum& o) {
		v -= o.v;
		if (v < 0) v += MOD;
		return *this;
	}
	modnum& operator *= (const modnum& o) {
		v = int(ll(v) * ll(o.v) % MOD);
		return *this;
	}
	modnum& operator /= (const modnum& o) {
		return *this *= o.inv();
	}

	friend modnum operator ++ (modnum& a, int) { modnum r = a; ++a; return r; }
	friend modnum operator -- (modnum& a, int) { modnum r = a; --a; return r; }
	friend modnum operator + (const modnum& a, const modnum& b) { return modnum(a) += b; }
	friend modnum operator - (const modnum& a, const modnum& b) { return modnum(a) -= b; }
	friend modnum operator * (const modnum& a, const modnum& b) { return modnum(a) *= b; }
	friend modnum operator / (const modnum& a, const modnum& b) { return modnum(a) /= b; }
};

template <typename T> T pow(T a, long long b) {
	assert(b >= 0);
	T r = 1; while (b) { if (b & 1) r *= a; b >>= 1; a *= a; } return r;
}

using num = modnum<998244353>;

vector<num> fact, ifact, p2;

void init(){
	int N = 410;
	fact = {1};
	for(int i = 1; i < N; i++) fact.push_back(i * fact[i-1]);
	ifact.resize(N);
	ifact.back() = 1 / fact.back();
	for(int i = N - 1; i > 0; i--) ifact[i-1] = i * ifact[i];
	p2 = {1};
	for(int i = 1; i < N; i++) p2.push_back(2 * p2.back());
}

num ncr(int n, int k){
	if(k < 0 || k > n) return 0;
	return fact[n] * ifact[k] * ifact[n-k];
}

vector<num> combine(vector<num> a, vector<num> b){
	vector<num> c(a.size() + b.size() - 1, 0);
	for(size_t i = 0; i < a.size(); i++) for(size_t j = 0; j < b.size(); j++) c[i + j] += a[i] * b[j];
	return c;
}

pair<vector<num>, vector<num> > solve(vector<int> h){
	if(h == vector<int>({0})){
		return {{0, 1}, {1, 0}};
	}
 	int k = (int)h.size();
	for(int& x : h) x -= 1;
	h.insert(h.begin(), 0);
	h.insert(h.end(), 0);
	vector<vector<int> > subarrays;
	vector<int> cur;
	int nzero = -2;
	for(int x : h){
		if(x == 0){
			if(!cur.empty()){
				subarrays.push_back(cur);
				cur = {};
			}
			nzero++;
		} else {
			cur.push_back(x);
		}
	}
	for(int j = 0; j < nzero; j++) subarrays.push_back({0});

	vector<num> combined_no_empty = {1};
	vector<num> combined_empty = {1};
	for(vector<int> x : subarrays){
		auto f = solve(x);
		combined_no_empty = combine(combined_no_empty, f.first);
		combined_empty = combine(combined_empty, f.second);
	}
	assert((int)combined_no_empty.size() == k+1);
	assert((int)combined_empty.size() == k+1);

	vector<num> res_no_empty(k+1, 0);
	vector<num> res_empty(k+1, 0);
	for(int i = 0; i <= k; i++){
		for(int j = 0; j <= i; j++){
			res_no_empty[i-j] += combined_no_empty[i] * ncr(i, j) * p2[k-i];
			res_empty[i-j] += combined_empty[i] * ncr(i, j) * p2[k-i];
		}
		res_empty[i] -= combined_empty[i];
		res_empty[i] += combined_no_empty[i];
	}

	return {res_no_empty, res_empty};
}

int main(){
	ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	init();
	int n;
	cin >> n;
	vector<int> h(n);
	for(int i = 0; i < n; i++) cin >> h[i];
	auto ans = solve(h);
	num res = ans.second[0];
	cout << res << '\n';
}

Measured memory_bytes: 5384