#include <bits/stdc++.h>
#define file(x) {freopen(x".in", "r", stdin); freopen(x".out", "w", stdout);}
template<typename T>
inline T chkmin(T& x, const T& y){if (x > y) x = y; return x;}
template<typename T>
inline T chkmax(T& x, const T& y){if (x < y) x = y; return x;}
#define rep(x, a) memset(x, a, sizeof x);
#define cls(x) rep(x, 0)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef pair<int, int> pii;
const int N = 45, _M_ = 12345, base = 1331, P = 1e9+7;
int n, m, a[N], siz[N], fac[N*N], ifac[N*N], Bx[N], id[N][N], ans;
inline int qpow(int a, int n)
{
	int ans = 1;
	while (n)
	{
		if (n & 1) ans = 1ll * ans * a % P;
		a = 1ll * a * a % P; n >>= 1;
	} return ans;
}
inline void initfac(int n)
{
	fac[0] = 1;
	for (int i=1; i<=n; i++) fac[i] = 1ll * i * fac[i-1] % P;
	ifac[n] = qpow(fac[n], P-2);
	for (int i=n-1; i>=0; i--) ifac[i] = 1ll * ifac[i+1] * (i+1) % P;
}
inline int A(int n, int m){return n<m ? 0 : 1ll * fac[n] * ifac[n-m] % P;}
int now, tt[N], B[N], v[N][_M_][N], e[N][_M_], dp[N][_M_];
unordered_map<ull, int> M[N];
void dfs(int b, int st, int lst)
{
	if (lst * (now - st + 1) > b) return ;
	if (st > now)
	{
		ull hash = 0;
		for (int i=1; i<st; i++) hash = hash * base + B[i];
		M[now][hash] = ++tt[now];
		for (int i=1; i<st; i++)
		{
			v[now][tt[now]][i] = B[i];
			e[now][tt[now]] += 1ll * B[i] * (B[i]-1) / 2;
		}
		return ;
	}
	if (st == now){B[st] = b; dfs(0, st+1, 0); return ;}
	for (int i=lst; i<=b; i++){B[st] = i; dfs(b-i, st+1, i);}
}
int main()
{
    scanf("%d", &n); initfac(a[1] = n*(n-1)/2);
    for (int i=n; i>1; i--) scanf("%d", a+i);
    for (int i=1; i<=n; i++){now = i; dfs(n, 1, 1);}
    dp[n][1] = 1;
	for (int i=n; i>1; i--)
		for (int s=1; s<=tt[i]; s++)
		{
			dp[i][s] = 1ll * dp[i][s] * A(e[i][s]-a[i+1], a[i]-a[i+1]-1) % P;
			memset(id, 0, sizeof id);
			for (int j=1; j<=i; j++) B[j] = v[i][s][j];
			for (int u=1; u<=i; u++)
				for (int v=u+1; v<=i; v++)
				{
					if (!id[B[u]][B[v]])
					{
						int top = 0;
						for (int p=1; p<=i; p++)
							if ((p != u) && (p != v)) Bx[++top] = B[p];
						Bx[++top] = B[u] + B[v];
						for (int p=top-1; p; p--) // a part of insertion sort
							if (Bx[p] > Bx[p+1]) swap(Bx[p], Bx[p+1]);
							else break;
						ull hash = 0;
						for (int p=1; p<=top; p++) hash = hash * base + Bx[p];
						id[B[u]][B[v]] = M[i-1][hash];
					}
					(dp[i-1][id[B[u]][B[v]]] += 1ll * dp[i][s] * B[u] % P * B[v] % P) %= P;
				}
		}
	printf("%d\n", dp[1][1] = 1ll * dp[1][1] * A(e[1][1] - a[2], a[1] - a[2] - 1) % P);
	return 0;
}