#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)

typedef long long ll;
ll mo = 1000000007;
//-----------------------------------------------------------------
ll combi(ll N_, ll C_) {
	const int NUM_ = 2000001;
	static ll fact[NUM_ + 1], factr[NUM_ + 1], inv[NUM_ + 1];
	if (fact[0] == 0) {
		inv[1] = fact[0] = factr[0] = 1;
		for (int i = 2; i <= NUM_; ++i) inv[i] = inv[mo % i] * (mo - mo / i) % mo;
		for (int i = 1; i <= NUM_; ++i) fact[i] = fact[i - 1] * i%mo, factr[i] = factr[i - 1] * inv[i] % mo;
	}
	if (C_<0 || C_>N_) return 0;
	return factr[C_] * fact[N_] % mo*factr[N_ - C_] % mo;
}
//-----------------------------------------------------------------
ll nHk(ll n, ll k)
{
	return combi(n + k - 1, k - 1);
}
//-----------------------------------------------------------------
int M;
vector<int> H;
//-----------------------------------------------------------------
int main() {
	cin >> M;

	int x;
	while(cin >> x) H.push_back(x);

	if (H.size() == 1 && H[0] == 0) {
		printf("1\n");
		return 0;
	}

	int sum = 0;
	rep(i, 0, H.size()) sum += H[i];
	int a = M - sum - (H.size() - 1);
	int b = H.size() + 1;

	if (a < 0) {
		cout << "NA" << endl;
		return 0;
	}

	//cout << a << endl;
	//cout << b << endl;
	
	ll ans = nHk(a, b);
	cout << ans << endl;
}