#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,a,b) for(int i=int(a);i<int(b);i++)
struct mint{
    static constexpr int  m = 998244353;
    int x;
    mint() : x(0){}
    mint(ll x_):x(x_%m){if(x<0)x+=m;}
    mint &operator+=(mint b){if((x+=b.x)>=m)x-=m; return *this;}
    mint &operator-=(mint b){if((x-=b.x)<0)x+=m; return *this;}
    mint &operator*=(mint b){x=ll(x)*b.x%m; return *this;}
    mint pow(ll e) const {
        mint r = 1,b =*this;
        while(e){
            if(e&1) r*=b;
            b*=b;
            e>>=1;
        }
        return r;
    }
    mint inv(){return pow(m-2);}
    mint &operator/=(mint b){return *this*=b.pow(m-2);}
    friend mint operator+(mint a,mint b){return a+=b;}
    friend mint operator-(mint a,mint b){return a-=b;}
    friend mint operator/(mint a,mint b){return a/=b;}
    friend mint operator*(mint a,mint b){return a*=b;}
};


int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
	cin>>N;
	vector<ll> A(N);
	rep(i,0,N) cin>>A[i];
	int L=(1<<20);
	vector<mint> fact(L,1),fact_inv(L,1);
	rep(i,1,L) fact[i]=fact[i-1]*i;
	fact_inv[L-1]=fact[L-1].inv();
	for(int i=L-1;i>0;i--) fact_inv[i-1]=fact_inv[i]*i;
	auto comb=[&](ll a,ll b) -> mint {
		if(a<0||a<b) return 0;
		return fact[a]*fact_inv[b]*fact_inv[a-b];
	};
	assert(N<=20);
	mint ans=0;
	rep(i,1,1<<N){
		mint tmp=1;
		ll B=-1;
		rep(j,0,N){
			if(i&(1<<j)){
				if(B!=-1){
					tmp*=comb(B,A[j]);
				}
				B=A[j];
			}
		}
		ans+=tmp;
	}
	cout<<ans.x<<"\n";
}