import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		solver();
	}

	final static long MOD = 1_000_000_007;

	static void solver() {
		Scanner sc = new Scanner(System.in);
		int m = Integer.parseInt(sc.nextLine());
		String[] s = sc.nextLine().split(" ");
		int[] num = new int[s.length];
		int res = m;
		for (int i = 0; i < s.length; i++) {
			num[i] = new Integer(s[i]);
			res -= num[i];
		}
		if (num[0] == 0) {
			System.out.println(1);
			return;
		}
		int n = num.length;

		res -= n - 1;
		if (res >= 0) {
			System.out.println(nCk(res + n , res));
		} else {
			System.out.println("NA");
		}
	}

	static long nCk(int n, int k) {
		if (n < k)
			return 0;
		else {
			return (fact(n) % MOD * inv(fact(n - k), MOD) % MOD * inv(fact(k), MOD) % MOD);
		}
	}

	static long fact(int n) {
		long ans = 1;
		for (int i = 1; i <= n; i++) {
			ans *= i;
			ans %= MOD;
		}
		return ans;
	}

	static void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	static long inv(long a, long mod) {
		a = a % mod;
		long b = mod;
		long p = 1, q = 0;

		while (b > 1) {
			long c = b / a;
			b = b % a;
			q = q - p * c;
			long d = b;
			b = a;
			a = d;
			d = p;
			p = q;
			q = d;
		}
		while (q < 0)
			q += mod;
		return q;
	}
}