#include <cstdlib>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <map>
#include <stack>
#include <vector>
#include <map>
#include <queue>
#include <ctime>
#include <algorithm>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef unsigned int uint;
const int inf=1061109567;
const int maxn=100010;
const int maxm=5010;
const int mod=998244353;
const double pi=3.14;

ll C[maxm][maxm];
ll f[maxn],s[maxn];

int main()
{
    freopen("asm_formation.in","r",stdin);
    freopen("asm_formation.out","w",stdout);
    //clock_t st=clock();
    C[0][0]=1;
    for(int i=1;i<=5000;i++)
    {
        C[i][0]=1;
        for(int j=1;j<=i;j++)
        {
            C[i][j]=(C[i-1][j-1]+C[i-1][j])%mod;
        }
    }
    int n,t;scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&t);
        s[i]=s[i-1]+t;
    }f[1]=1;
    for(int i=2;i<=n;i++)
    {
        f[i]=(f[i-1]*C[s[i]-1][s[i]-s[i-1]-1])%mod;
    }
    printf("%lld\n",f[n]%mod);
    //clock_t ed=clock();
    //printf("\nTime used : %.5lf Ms\n",double(ed-st)/CLOCKS_PER_SEC);
    return 0;
}