#include <algorithm>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#define ll long long
#define o1 first
#define o2 second
#define omp make_pair
#define opb push_back
#define opc pop_back()
#define inf 3423423423423423422ll
#define MAX_N 5222

using namespace std;

ll read(){ll x = 0;char c = 0;bool v = 0;do{c = getchar();if(c == '-')v = 1;} while(c < '0' || c > '9');do{x = (x << 3) + (x << 1) + c - '0';c = getchar();} while(c >= '0' && c <= '9');return v ? -x : x;}
char gtc(){char c = 0;while(c < 33)c = getchar();return c;}

const ll P = 998244353;

int n;
int a[MAX_N];
ll dp[MAX_N][2], dps[MAX_N], dpl[MAX_N][2];

void oM()
{
    int m = read();
    n = 0;
    for(int i = 1; i <= m; i++)
    {
        int k = read();
        for(int j = 1; j <= k; j++)
            a[++n] = i;
    }
    dp[0][0] = 1;
    for(int i = 1; i <= n; i++)
    {
        for(int j = 0; j <= i; j++)
        {
            dpl[j][0] = dp[j][0], dpl[j][1] = dp[j][1];
            if(i == 1 || a[i] != a[i - 1])
                dpl[j][0] = (dp[j][0] + dp[j][1]) % P, dpl[j][1] = 0;
            dp[j][0] = dp[j][1] = 0;
            dps[j] = (dpl[j][0] + (j ? dps[j - 1] : 0)) % P;
        }
        for(int j = 1; j <= i; j++)
            dp[j][0] = (dps[i] - dps[j - 1] + P) % P;
        for(int j = 1; j <= i; j++)
            dp[j][1] = (dpl[j - 1][1] + dpl[j - 1][0]) % P;
        /*for(int j = 1; j <= i; j++)
            printf("%lld ", dp[j][0]);
        printf("\n");
        for(int j = 1; j <= i; j++)
            printf("%lld ", dp[j][1]);
        printf("\n");*/
    }
    ll ans = 0;
    for(int i = 0; i <= n; i++)
        ans = (ans + dp[i][0] + dp[i][1]) % P;
    printf("%lld\n", ans);
}

void oC()
{
    ;
}

void oE()
{
    ;
}

int main()
{
    //freopen("preface.in", "r", stdin);
    //freopen("preface.out", "w", stdout);
    oE();
    int T = 1;
    while(T--)
        oM(), oC();
    return 0;
}