#include<bits/stdc++.h>
using namespace std;
#define rep(i,x,y) for (int i=(x);i<=(y);i++)
#define drep(i,y,x) for (int i=(y);i>=(x);i--)
#define pii pair<int,int>
#define fir first
#define sec second
#define MP make_pair
template<typename T> bool chkmin(T &x, T y){return x>y?x=y,1:0;}
template<typename T> bool chkmax(T &x, T y){return x<y?x=y,1:0;}
void file() {
    #ifdef zqj
    freopen("a.in","r",stdin);
    #endif
}
typedef long long ll;
#define sz 505
const ll mod = 998244353;

int n,m;
int a[sz],s[sz];

int dp[2][sz][sz];

int main() {
    file();
    cin>>n;
    rep(i,1,n) cin>>a[i],m+=a[i],s[i]=s[i-1]+a[i];
    while (!a[n]) --n;
    dp[0][0][0]=1;
    int cur=0;
    rep(i,0,m-1) {
        rep(j,0,n) rep(k,0,a[j]) dp[cur^1][j][k]=0;
        rep(j,0,n) {
            ll tot=0;
            rep(k,0,a[j]) {
                ll w=dp[cur][j][k];
                if (!w) continue;
                if (k!=a[j]) (dp[cur^1][j][k+1]+=w)%=mod;
                if (j&&i-k!=s[j-1]) (dp[cur^1][j][k]+=w)%=mod;
                tot+=w;
            }
            tot%=mod;
            rep(j_,j+1,n) if (a[j_]) (dp[cur^1][j_][1]+=tot)%=mod;
        }
        cur^=1;
    }
    cout<<dp[cur][n][a[n]]<<'\n';
    return 0;
}