#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using vi = vector<int>;    using vvi = vector<vi>;
using vb = vector<bool>;   using vvb = vector<vb>;
using vl = vector<ll>;     using vvl = vector<vl>;
using vd = vector<double>; using vvd = vector<vd>;

#define REP(i,n) for(ll i = 0; i < (n); ++i)
#define ALL(c) (c).begin(), (c).end()
#define FOR(i,s,e) for (ll i = s; i < (ll)e; i++)
#define TEN(x) ((ll)1e##x)

ll inverse(ll v, ll mod) {
	ll a = v, b = mod, x = 1, y = 0;
	while (b) {
		ll t = a / b;
		swap(a -= t * b, b);
		swap(x -= t * y, y);
	}
	return (x % mod + mod) % mod;
}

ll nCr(ll n,ll r, ll mod){
	if(n < r) return 0;
	r = min(r,n-r);
	ll ret = 1;
	REP(i, r) {
		(ret *= n - i) %= mod;
		(ret *= inverse(i + 1, mod)) %= mod;
	}
	return ret;
}

int main() {
#ifdef _WIN32
	ifstream cin("sample.in");
	ofstream cout("sample.out");
#endif
	cin.tie(0); // cinとcoutの連携を切る
	ios_base::sync_with_stdio(false);
	cout << fixed << setprecision(50);
	ll m;
	cin >> m;
	vl h;
	{
		ll tmp;
		while (cin >> tmp) h.push_back(tmp);
	}

	if (h[0] == 0) {
		cout << 1 << endl;
		return 0;
	}

	ll sum = -1;
	REP(i, h.size()) sum += h[i] + 1;
	ll diff = m - sum;
	if (diff < 0) {
		cout << "NA" << endl;
		return 0;
	}

	ll mod = TEN(9) + 7;
	cout << nCr(diff + h.size(), diff, mod) << endl;
	return 0;
}