#include <iostream>
#include <cstdio>
using namespace std;
typedef long long ll;
const int N=5e2+10;
const int Sigma=1.5e3+10;
const ll P=1e9+7;
int n;
ll a[N],s[N],fact[N],C[Sigma][Sigma],f[N][Sigma];

int main() {
    freopen("photo.in","r",stdin);freopen("photo.out","w",stdout);
    scanf("%d",&n);
    fact[0]=C[0][0]=1;
    for (int i=1;i<N;i++) fact[i]=fact[i-1]*i%P;
    for (int i=1;i<Sigma;i++)
        for (int j=0;j<=i;j++)
            C[i][j]=(C[i-1][j]+(j?C[i-1][j-1]:0))%P;
    for (int i=1;i<=n;i++) scanf("%lld",&a[i]),s[i]=s[i-1]+a[i];
    f[1][s[1]-1]=1;
    for (int i=2;i<=n;i++)
        for (int j=0;j<=s[i-1];j++)
            if (f[i-1][j])
                for (int k=1;k<=a[i];k++)
                    for (int t=0;t<=min(k,j);t++)
                        (f[i][j+a[i]-k-t]+=f[i-1][j]*C[j][t]%P*C[a[i]-1][k-1]%P*C[s[i-1]+1-j][k-t]%P)%=P;
    for (int i=1;i<=n;i++) (f[n][0]*=fact[a[i]])%=P;
    printf("%lld\n",f[n][0]);
}