tree

//misaka and elaina will carry me to red

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

#include <iostream>
#include <cmath>
#include <utility>
#include <cassert>
#include <algorithm>
#include <vector>
#include <array>
#include <cstdio>
#include <cstring>
#include <functional>
#include <numeric>
#include <set>
#include <queue>
#include <map>
#include <chrono>
#include <random>

#define sz(x) ((int)(x.size()))
#define all(x) x.begin(), x.end()
#define pb push_back
#define eb emplace_back
#define kill(x, s) {if(x){ cout << s << "\n"; return ; }}

#ifndef LOCAL
#define cerr while(0) cerr
#endif

using ll = long long;
using lb = long double;

const lb eps = 1e-9;
const ll mod = 1e9 + 7, ll_max = 1e18;
//const ll mod = (1 << (23)) * 119 +1, ll_max = 1e18;
const int MX = 500 +10, int_max = 0x3f3f3f3f;

struct {
  template<class T>
  operator T() {
    T x; std::cin >> x; return x;
  }
} in;

using namespace std;

ll dp[2][MX][MX*2][4];
ll fac[MX*2], ifac[MX*2];
int deg[MX];

ll binpow(ll a, ll b = mod - 2){
    ll ans = 1;
    for(int i = 1; i<=b; i*=2ll){
        if(i&b) (ans *= a) %= mod;
        (a *= a) %= mod;
    }
    return ans;
}

void solve(){
    int n = in;
    int leaf = 0;
    kill(n == 1, 0);
    kill(n == 2, 1);
    fac[0] = 1;
    ifac[0] = 1;
    for(int i = 0; i<n; i++){
        deg[i] = in;
        if(deg[i] == 1) leaf++;
    }
    for(int i = 1; i<=n*2; i++){
        fac[i] = 1ll*i*fac[i-1]%mod;
        ifac[i] = binpow(fac[i]);
    }
    dp[0][0][0][0] = 1;
    int sum = 0;
    int r = 0;
    for(int i = 0; i<n; i++){
        for(int j = 0; j<=i; j++){
            for(int k = 0; k<=sum; k++){
                for(int h = 0; h<2; h++){
                    for(int l = 0; l<4; l+=2){
                        //add to left side
                        ll v = dp[r][j][k][h + l];
                        (dp[r^1][j+1][k + deg[i]][h + l] += ifac[deg[i]-1] * v%mod) %= mod;
                        //add to right side
                        (dp[r^1][j][k][h + l] += ifac[deg[i]-1] * v%mod) %= mod;
                        if(deg[i] > 1){
                            if (h == 0){
                                // add as left tree endpoint
                                (dp[r^1][j + 1][k + deg[i] - 1][1 + l] += ifac[deg[i] - 2] * v % mod) %= mod;
                            }
                            if(l == 0){
                                //add as right tree endpoint
                                (dp[r^1][j][k][h + 2] += ifac[deg[i] - 2] * v % mod) %= mod;
                            }
                        }
                    }
                }
            }
        }
        r ^= 1;
        for(int j = 0; j<=n; j++){
            for(int k = 0; k<=2*n-2; k++){
                for(int hl = 0; hl<4; hl++){
                    dp[r^1][j][k][hl] = 0;
                }
            }
        }
        sum += deg[i];
    }
    ll ans = 0;
    for(int j = 2; j<=n-2; j++){
        int t = min(j, n - j);
        ans += 1ll * t * fac[n - j - 2] % mod * fac[j - 2] % mod * dp[r][j][2 * j - 2][3] % mod;
    }
    ans %= mod;
    ll tot = fac[n-2];
    for(int i = 1; i<=n; i++){
        tot *= ifac[deg[i-1]-1];
        tot %= mod;
    }
    ans += 2ll*tot*leaf%mod;
    ans %= mod;
    cerr << ans << " " << tot << "\n";
    cout << ans*binpow(2ll*tot%mod)%mod << "\n";
}

signed main(){
  cin.tie(0) -> sync_with_stdio(0);

  int T = 1;
  //cin >> T;
  for(int i = 1; i<=T; i++){
        //cout << "Case #" << i << ": ";
        solve();
    }
  return 0;
}