// Hallelujah, praise the one who set me free
// Hallelujah, death has lost its grip on me
// You have broken every chain, There's salvation in your name
// Jesus Christ, my living hope
#include <bits/stdc++.h> 
using namespace std;

#define REP(i, s, e) for (int i = (s); i < (e); i++)
#define RREP(i, s, e) for (int i = (s); i >= (e); i--)
template <class T>
inline bool mnto(T& a, T b) {return a > b ? a = b, 1 : 0;}
template <class T>
inline bool mxto(T& a, T b) {return a < b ? a = b, 1: 0;}

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
#define FI first
#define SE second
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
typedef tuple<int, int, int> iii;
#define ALL(_a) _a.begin(), _a.end()
#define SZ(_a) (int) _a.size()
#define pb push_back
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;
typedef vector<iii> viii;

#ifndef DEBUG
#define cerr if (0) cerr
#endif

const int INF = 1000000005;
const ll LINF = 1000000000000000005ll;
const int MAXN = 505;
const int MOD = 998244353;

#define submod(x) if (x >= MOD) x -= MOD
#define addmod(x) if (x < 0) x += MOD

int n;
vi v;
int nxt[MAXN];
int dp[MAXN][MAXN];
int ans;

int main() {
#ifndef DEBUG
    ios::sync_with_stdio(0), cin.tie(0);
#endif
    cin >> n;
    v.pb(-1);
    REP (i, 0, n) {
        int a; cin >> a;
        REP (j, 0, a) {
            v.pb(i);
        }
    }
    n = SZ(v) - 1;
    nxt[n] = n;
    RREP (i, n - 1, 1) {
        if (v[i + 1] != v[i]) {
            nxt[i] = i;
        } else {
            nxt[i] = nxt[i + 1];
        }
    }
    dp[nxt[1]][0] = 1;
    REP (i, nxt[1], n) {
        REP (j, 0, i) {
            if (dp[i][j] == 0) {
                continue;
            }
            dp[nxt[i + 1]][j] += dp[i][j];
            submod(dp[nxt[i + 1]][j]);
            REP (k, j + 1, i + 1) {
                dp[i + 1][k] += dp[i][j];
                submod(dp[i + 1][k]);
            }
        }
    }
    REP (j, 0, n) {
        ans += dp[n][j];
        submod(ans);
    }
    cout << ans << '\n';
    return 0;
}