#include<cstdio>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<map>
using namespace std;
typedef long long LL;
const LL mod=1e9+7;int n;
struct zhuangtai
{int u[50];friend bool operator >(zhuangtai z1,zhuangtai z2){if(z1.u[0]==z2.u[0]){for(int i=1;i<=z1.u[0];i++)if(z1.u[i]!=z2.u[i])return z1.u[i]>z2.u[i];}return z1.u[0]>z2.u[0];}friend bool operator <(zhuangtai z1,zhuangtai z2){if(z1.u[0]==z2.u[0]){for(int i=1;i<=z1.u[0];i++)if(z1.u[i]!=z2.u[i])return z1.u[i]<z2.u[i];}return z1.u[0]<z2.u[0];}int getsum(){int ret=0;for(int i=1;i<=u[0];i++)ret=(ret+(u[i]*(u[i]-1)/2)%mod)%mod;return ret;}
}mp[41000];int z,g[50];
bool cmp(zhuangtai z1,zhuangtai z2){return z1>z2;}
map<zhuangtai,int>id;//通过状态找编号
void dfs(int d,int last)//预处理拆分n的方案
{if(d==n){z++;for(int i=0;i<=g[0];i++)mp[z].u[i]=g[i];return ;}for(int i=last;i+d<=n;i++) {g[++g[0]]=i;dfs(i+d,i);g[g[0]--]=0;}
}LL quick_pow(LL A,LL p)
{LL ret=1;while(p!=0){if(p%2==1)ret=ret*A%mod;A=A*A%mod;p/=2;}return ret;
}
LL fac[110000],fac_inv[110000];
LL getP(int n,int m){return fac[n]*fac_inv[n-m]%mod;}zhuangtai t;int h[50];
int getnzt(int zt,int x,int y)
{memcpy(h,mp[zt].u,sizeof(h));int d=h[x]+h[y]; memset(t.u,0,sizeof(t.u));for(int i=1;i<=h[0];i++){if(i!=x&&i!=y){if(d!=-1&&h[i]>d)t.u[++t.u[0]]=d,d=-1;t.u[++t.u[0]]=h[i];}}if(d!=-1)t.u[++t.u[0]]=d;return id[t];
}
int a[50];LL f[41000];
int main()
{fac[0]=1,fac_inv[0]=1;for(int i=1;i<=100000;i++)fac[i]=fac[i-1]*i%mod,fac_inv[i]=quick_pow(fac[i],mod-2);scanf("%d",&n);for(int i=1;i<n;i++)scanf("%d",&a[i]);z=0;dfs(0,1);sort(mp+1,mp+z+1,cmp);for(int i=1;i<=z;i++)id[mp[i]]=i;memset(f,0,sizeof(f));f[1]=1;for(int zt=1;zt<=z;zt++)if(f[zt]>0){int e=n-mp[zt].u[0]+1;//轮到第几条边用来合并LL P=getP(mp[zt].getsum()-(a[e-1]),a[e]-a[e-1]-1);//两条树边中间其他边选择的方案数 for(int i=1;i<=mp[zt].u[0];i++)for(int j=i+1;j<=mp[zt].u[0];j++){int nzt=getnzt(zt,i,j);f[nzt]=(f[nzt]+f[zt]*P%mod*mp[zt].u[i]%mod*mp[zt].u[j]%mod)%mod;}}int rst=n*(n-1)/2-a[n-1];printf("%lld\n",f[z]*getP(rst,rst)%mod);return 0;
}