/* template.cpp [[[ */
#include <bits/stdc++.h>
using namespace std;
#define get_macro(a, b, c, d, name, ...) name
#define rep(...) get_macro(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep(...) get_macro(__VA_ARGS__, rrep4, rrep3, rrep2, rrep1)(__VA_ARGS__)
#define rep1(n) rep2(i_, n)
#define rep2(i, n) rep3(i, 0, n)
#define rep3(i, a, b) rep4(i, a, b, 1)
#define rep4(i, a, b, s) for (ll i = (a); i < (ll)(b); i += (ll)s)
#define rrep1(n) rrep2(i_, n)
#define rrep2(i, n) rrep3(i, 0, n)
#define rrep3(i, a, b) rrep4(i, a, b, 1)
#define rrep4(i, a, b, s) for (ll i = (ll)(b) - 1; i >= (ll)(a); i -= (ll)s)
#define each(x, c) for (auto &&x : c)
#define fs first
#define sc second
#define all(c) begin(c), end(c)
using ui = unsigned;
using ll = long long;
using ul = unsigned long long;
using ld = long double;
const int inf = 1e9 + 10;
const ll inf_ll = 1e18 + 10;
const ll mod = 1e9 + 7;
const ll mod9 = 1e9 + 9;
const int dx[]{-1, 0, 1, 0, -1, 1, 1, -1};
const int dy[]{0, -1, 0, 1, -1, -1, 1, 1};
template<class T, class U> void chmin(T &x, const U &y){ x = min<T>(x, y); }
template<class T, class U> void chmax(T &x, const U &y){ x = max<T>(x, y); }
struct prepare_ { prepare_(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(12); } } prepare__;
ll in(){ ll x; cin >> x; return x; }
vector<ll> in(size_t n){ vector<ll> v(n); each(x, v) cin >> x; return v; }
/* ]]] */

int n;
vector<int> a;

ll power(ll x, ll y){
  ll s = 1;
  while (y > 0){
    if (y & 1) s = s * x % mod;
    x = x * x % mod;
    y >>= 1;
  }
  return s;
}

ll inv(ll x){
  return power(x, mod - 2);
}

int main(){
  cin >> n;
  int x, y;
  while (cin >> x) a.push_back(x);
  if (a[0] == 0) cout << "1\n", exit(0);
  x = a.size() + (n - accumulate(all(a), 0) - (int)a.size() + 1);
  y = a.size();
  if (x < y) cout << "NA\n", exit(0);
  ll res = 1;
  rep(i, y) res = res * (x - i) % mod;
  rep(i, y) res = res * inv(i + 1) % mod;
  cout << res << endl;
}