#include <bits/stdc++.h>
using namespace std;

#define int long long

const int MOD = 1000000000 + 7;

int Factorial(int n)
{
	int res = 1;
	while (n) (res *= n--) %= MOD;
	return res;
}

int Pow(int x, int n)
{
	if (n == 0) return 1;
	int res = Pow(x*x % MOD, n/2);
	if (n&1) res *= x;
	return res % MOD;
}

int Inverse(int n)
{
	return Pow(n, MOD - 2);
}

int H(int ball, int stick)
{
	return Factorial(ball + stick) * Inverse(Factorial(ball) * Factorial(stick) % MOD) % MOD;
}

int M;

signed main()
{
	cin >> M;
	int h, sum = 0, N = 0;
	while (cin >> h)
	{
		sum += h;
		N++;
	}
	if (h == 0) sum = 0, N = 0;
	if (sum + N - 1 > M)
	{
		puts("NA");
		return 0;
	}
	int n = M - (sum + N - 1), k = N;
	printf("%lld\n", H(n, k));
	return 0;
}