#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <atcoder/modint>

using namespace std;
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
const i64 INF = 1001001001001001001;

using Modint = atcoder::static_modint<998244353>;



Modint I[1024];

void extend(int newN = 1000){
    std::vector<Modint> F(newN+1, Modint(1));
    std::vector<Modint> iF(newN+1, Modint(1));
    for(int i=1; i<=newN; i++) F[i] = F[i-1] * Modint::raw(i);
    iF[newN] = F[newN].inv();
    for(int i=newN; i>=1; i--) iF[i-1] = iF[i] * Modint::raw(i);
    for(int i=1; i<=newN; i++) I[i] = F[i-1] * iF[i];
}

Modint factorial(int n){
    Modint x = 1;
    for(int i=1; i<=n; i++) x *= Modint::raw(i);
    return x;
}

pair<Modint, int> hook(string s){
    vector<int> A, B;
    int a = 0, b = 0;
    for(char c : s) if(c == '0') a++;
    for(char c : s){
        if(c == '0'){ B.push_back(b); a--; }
        if(c == '1'){ A.push_back(a); b++; }
    }
    reverse(B.begin(), B.end());
    int lambda = 0;
    for(int a : A) lambda += a;
    Modint ans = 1;
    int cnt = 0;
    rep(i,A.size()) rep(j,B.size()){
        if(A[i] <= j || B[j] <= i) continue;
        ans *= I[A[i] + B[j] - i - j - 1];
        cnt++;
    }
    return { ans, cnt };
}


int main(){
    extend();
    int N; cin >> N;
    vector<int> A(N+1); rep(i,N) cin >> A[i+1];
    string S;
    rep(i,N){
        rep(j,A[i+1]-A[i]) S.push_back('1');
        S.push_back('0');
    }

    string S2[2];
    rep(i,S.size()) S2[i%2].push_back(S[i]);
    auto ans0 = hook(S2[0]);
    auto ans1 = hook(S2[1]);
    Modint ans = factorial(ans0.second + ans1.second) * ans0.first * ans1.first;

    rep(t,2) sort(S2[t].begin(), S2[t].end());

    string S3;
    rep(i,S.size()) S3.push_back(S2[i%2][i/2]);

    if(S3.find("10") != string::npos) ans = 0;
    cout << ans.val() << '\n';
    return 0;
}


struct ios_do_not_sync{
    ios_do_not_sync(){
        std::ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
    }
} ios_do_not_sync_instance;