#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
 
#include <bits/stdc++.h>
 
using namespace std;
 
typedef double db;
typedef long long ll;
typedef long double ld;
typedef string str;
 
typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;
typedef complex<ld> cd;
 
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<ld> vd;
typedef vector<str> vs;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
 
#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); i--)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a : x)
 
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
 
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define rsz resize
#define ins insert
 
const int MOD =  998244353; // 998244353 = (119<<23)+1
const ll INF = 1e18;
const int MX = 2e5+5;
const ld PI = 4*atan((ld)1);
 
template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
 
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
 
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>
 
using namespace __gnu_pbds;
using namespace __gnu_cxx;
 
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
 
#define ook order_of_key
#define fbo find_by_order
 
namespace input {
    template<class T> void re(complex<T>& x);
    template<class T1, class T2> void re(pair<T1,T2>& p);
    template<class T> void re(vector<T>& a);
    template<class T, size_t SZ> void re(array<T,SZ>& a);
 
    template<class T> void re(T& x) { cin >> x; }
    void re(double& x) { string t; re(t); x = stod(t); }
    void re(ld& x) { string t; re(t); x = stold(t); }
    template<class T, class... Ts> void re(T& t, Ts&... ts) { 
        re(t); re(ts...); 
    }
 
    template<class T> void re(complex<T>& x) { T a,b; re(a,b); x = cd(a,b); }
    template<class T1, class T2> void re(pair<T1,T2>& p) { re(p.f,p.s); }
    template<class T> void re(vector<T>& a) { F0R(i,sz(a)) re(a[i]); }
    template<class T, size_t SZ> void re(array<T,SZ>& a) { F0R(i,SZ) re(a[i]); }
}
 
using namespace input;
 
namespace output {
    void pr(int x) { cout << x; }
    void pr(long x) { cout << x; }
    void pr(ll x) { cout << x; }
    void pr(unsigned x) { cout << x; }
    void pr(unsigned long x) { cout << x; }
    void pr(unsigned long long x) { cout << x; }
    void pr(float x) { cout << x; }
    void pr(double x) { cout << x; }
    void pr(ld x) { cout << x; }
    void pr(char x) { cout << x; }
    void pr(const char* x) { cout << x; }
    void pr(const string& x) { cout << x; }
    void pr(bool x) { pr(x ? "true" : "false"); }
    template<class T> void pr(const complex<T>& x) { cout << x; }
    
    template<class T1, class T2> void pr(const pair<T1,T2>& x);
    template<class T> void pr(const T& x);
    
    template<class T, class... Ts> void pr(const T& t, const Ts&... ts) { 
        pr(t); pr(ts...); 
    }
    template<class T1, class T2> void pr(const pair<T1,T2>& x) { 
        pr("{",x.f,", ",x.s,"}"); 
    }
    template<class T> void pr(const T& x) { 
        pr("{"); // const iterator needed for vector<bool>
        bool fst = 1; for (const auto& a: x) pr(!fst?", ":"",a), fst = 0; 
        pr("}");
    }
    
    void ps() { pr("\n"); } // print w/ spaces
    template<class T, class... Ts> void ps(const T& t, const Ts&... ts) { 
        pr(t); if (sizeof...(ts)) pr(" "); ps(ts...); 
    }
    
    void pc() { pr("]\n"); } // debug w/ commas
    template<class T, class... Ts> void pc(const T& t, const Ts&... ts) { 
        pr(t); if (sizeof...(ts)) pr(", "); pc(ts...); 
    }
    #define dbg(x...) pr("[",#x,"] = ["), pc(x);
}
 
using namespace output;
 
namespace io {
    void setIn(string s) { freopen(s.c_str(),"r",stdin); }
    void setOut(string s) { freopen(s.c_str(),"w",stdout); }
    void setIO(string s = "") {
        cin.sync_with_stdio(0); cin.tie(0); // fast I/O
        cin.exceptions(cin.failbit); // ex. throws exception when you try to read letter into int
        if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
    }
}
 
using namespace io;
 
template<class T> T invGeneral(T a, T b) {
	a %= b; if (a == 0) return b == 1 ? 0 : -1;
	T x = invGeneral(b,a); 
	return x == -1 ? -1 : ((1-(ll)b*x)/a+b)%b;
}
 
template<class T> struct modular {
	T val; 
	explicit operator T() const { return val; }
	modular() { val = 0; }
	modular(const ll& v) { 
		val = (-MOD <= v && v <= MOD) ? v : v % MOD;
		if (val < 0) val += MOD;
	}
	
	// friend ostream& operator<<(ostream& os, const modular& a) { return os << a.val; }
	friend void pr(const modular& a) { pr(a.val); }
	friend void re(modular& a) { ll x; re(x); a = modular(x); }
   
	friend bool operator==(const modular& a, const modular& b) { return a.val == b.val; }
	friend bool operator!=(const modular& a, const modular& b) { return !(a == b); }
	friend bool operator<(const modular& a, const modular& b) { return a.val < b.val; }
 
	modular operator-() const { return modular(-val); }
	modular& operator+=(const modular& m) { if ((val += m.val) >= MOD) val -= MOD; return *this; }
	modular& operator-=(const modular& m) { if ((val -= m.val) < 0) val += MOD; return *this; }
	modular& operator*=(const modular& m) { val = (ll)val*m.val%MOD; return *this; }
	friend modular pow(modular a, ll p) {
		modular ans = 1; for (; p; p /= 2, a *= a) if (p&1) ans *= a;
		return ans;
	}
	friend modular inv(const modular& a) { 
		auto i = invGeneral(a.val,MOD); assert(i != -1);
		return i;
	} // equivalent to return exp(b,MOD-2) if MOD is prime
	modular& operator/=(const modular& m) { return (*this) *= inv(m); }
	
	friend modular operator+(modular a, const modular& b) { return a += b; }
	friend modular operator-(modular a, const modular& b) { return a -= b; }
	friend modular operator*(modular a, const modular& b) { return a *= b; }
	
	friend modular operator/(modular a, const modular& b) { return a /= b; }
};
 
typedef modular<int> mi;
typedef pair<mi,mi> pmi;
typedef vector<mi> vmi;
typedef vector<pmi> vpmi;

int N;
int curind = 0;
int h[405];
vi trans[405*405];
vector<mi> dpanses[405*405][2];
pair<int, pi> ranges[405*405]; //ycoor, leftx, rightx of region
mi tpow[405];
void gentpows(){
	tpow[0] = 1;
	for(int i = 1; i < 405; i++){
		tpow[i] = 2*tpow[i-1];
	}
}
/**
 * Description: pre-compute factorial mod inverses for $MOD$, 
 	* assumes $MOD$ is prime and $SZ < MOD$
 * Time: O(SZ)
 * Source: KACTL
 * Verification: https://dmoj.ca/problem/tle17c4p5
 */

vmi invs, fac, ifac;
void genFac(int SZ) {
	invs.rsz(SZ), fac.rsz(SZ), ifac.rsz(SZ); 
	invs[1] = fac[0] = ifac[0] = 1; 
	FOR(i,2,SZ) invs[i] = mi(-(ll)MOD/i*invs[MOD%i]);
	FOR(i,1,SZ) {
		fac[i] = fac[i-1]*i;
		ifac[i] = ifac[i-1]*invs[i];
	}
}
mi comb(int a, int b) {
	if (a < b || b < 0) return 0;
	return fac[a]*ifac[b]*ifac[a-b];
}

vmi mult(vmi a, vmi b){ // multiply 2 polynomials
	vmi c;
	c.rsz(sz(a)+sz(b)-1);
	for(int i = 0; i < sz(a); i++){
		for(int j = 0; j < sz(b); j++){
			c[i+j]+=a[i]*b[j];
		}
	}
	return c;
}
void getinds(int ycoor, int leftx, int rightx){ // considering tiles >=ycoor
	assert(leftx <= rightx);
	assert(ycoor <= N);
	
	curind++;
	int ind = curind;
	ranges[ind] = mp(ycoor, mp(leftx, rightx));
	int curleft = -1;
	bool incomp = 0;
	for(int i = leftx; i <= rightx+1; i++){ //+1 because to the right is always nothing
		if(h[i] < ycoor+1){ //component ends
			if(incomp == 1){
				trans[ind].pb(curind+1);
				getinds(ycoor+1, curleft, i-1);
				incomp = 0;
			}
		}
		else{
			if(incomp == 0){
				incomp = 1;
				curleft = i;
			}
		}
	}
}

void getdpanses(int ind){
	
	int leftx = ranges[ind].s.f;
	int rightx = ranges[ind].s.s;
	vmi anses[2];
	anses[0].rsz(rightx-leftx+2);
	anses[1].rsz(rightx-leftx+2);
	for(auto u: trans[ind]){
		getdpanses(u);
	}
	vmi curans[2] = {{1}, {1}};
	int restlength = 0;
	for(auto u: trans[ind]){
		curans[0] = mult(curans[0], dpanses[u][0]);
		curans[1] = mult(curans[1], dpanses[u][1]);
		restlength+=ranges[u].s.s-ranges[u].s.f+1;
	}
	restlength = (rightx-leftx+1)-restlength;
	vmi xpow;
	for(int i = 0; i < restlength; i++){
		xpow.pb(0);
	}
	xpow.pb(1);
	curans[0] = mult(curans[0], xpow);
	while(sz(curans[1]) < sz(curans[0])) curans[1].pb(0);
	//no rooks?
	//only rooks in R columns
	//some rooks in U columns
	int isize = rightx-leftx+1;
	for(int i = 0; i < sz(curans[0]); i++){
		assert(sz(curans[0]) == sz(curans[1]));
		for(int C1 = 0; C1 < 2; C1++){
			for(int j = i; j <= rightx-leftx+1; j++){
				for(int C2 = 0; C2 < 2; C2++){
					if(C1 == 0){
						if(C2 == 1) continue;
						//no empties, no empties. We can't put an empty row.
						//
						if(j == 0) continue;
						//j-i new rooks
						//2^i redundant possibilities
						
						if(i == j){
							//no new rooks are added
							//at least 1 redundant rook
							anses[C2][j]+=curans[C1][i]*(tpow[i]-1);
						}
						else{
							//j-i rooks in U-columns
							anses[C2][j]+=curans[C1][i]*(tpow[i])*comb(isize-i, j-i);
						}
					}
					else{
						if(C2 == 0){
							//no rooks in this row (must be empty)
							if(j == i) anses[C2][j]+=curans[C1][i];
						}
						else{
							// choose j-i 
							anses[C2][j]+=curans[C1][i]*(tpow[i])*comb(isize-i, j-i);
						}
					}
				}
			}
		}
	}
	dpanses[ind][0] = anses[0];
	dpanses[ind][1] = anses[1];
	/*
	for(int i = 0; i < sz(curans); i++){
		for(int j = i; j <= rightx-leftx+1; j++){
			// we added j-i new rooks in new columns
			// and some redundant rooks (out of i)
			
			if(i == j){
				//with rooks in bottom
				anses[j]+=(tpow[i]-1)*(curans[i]); // -1 because there must be a rook in bottom
				if(j == rightx-leftx+1){ //no rooks in bottom? only possible if all columns already filled
					anses[j]+=curans[i];
					
				}
				if(ind == 1 && i == 1 && j == 1){
					cout << "HI";
					cout << int((tpow[i]-1)*(curans[i]));
				}
			}
			else{
				anses[j]+=comb(rightx-leftx+1-i, j-i)*(tpow[i])*curans[i]; // choose this many more rooks
				if(ind == 1 && j == 2){
					ps(i, ":", comb(rightx-leftx+1-i, j-i)*(tpow[i])*curans[i]);
				}
			}
		}
	}
	dpanses[ind] = anses;
	
	for(int i = 0; i <= rightx-leftx+1){
		for(int j = 0; j < sz(curans); j++){
			
		}
	}*/
}
int main() {
	setIO();
	gentpows();
	genFac(500);
    // you should actually read the stuff at the bottom
    cin >> N;
    for(int i = 1; i <= N; i++){
    	cin >> h[i];
    }
    getinds(1, 1, N); // ycoor, leftx, rightx
    
    getdpanses(1);
    /*for(int i = 1; i <= N*N; i++){
    	ps(ranges[i], trans[i], dpanses[i]);
    }*/
    ps(dpanses[1][0][N]);
    /*
    mi ans = 0;
    for(auto u: dpanses[1]){
    	ans+=u;
    }
    cout << int(ans);*/
}
 
/* stuff you should look for
	* int overflow, array bounds
	* special cases (n=1?), set tle
	* do smth instead of nothing and stay organized
*/


Measured memory_bytes: 20480