#include <iostream>
using namespace std;

int main() {
	long long int m;
	scanf("%lld", &m);
	long long int *h = new long long int[m];
	long long int i = 0;
	long long int sum = 0;
	while (cin >> h[i]) {
		sum += h[i];
		i++;
	}
	long long int num = m - sum;
	num = num - i + 1;
	if (num < 0) {
		printf("NA\n");
	}
	else if (num == 0) {
		printf("1\n");
	}
	else {
		long long int fact1 = 1, fact2 = 1, fact3 = 1;
		long long int j = 1;
		for (j = 0; j < num + i; j++) {
			fact1 = (fact1 * (j + 1)) % 1000000007;
		}

		for (j = 0; j < i; j++) {
			fact2 = (fact2 * (j + 1)) % 1000000007;
		}

		for (j = 0; j < num; j++) {
			fact3 = (fact3 * (j + 1)) % 1000000007;
		}
		fact2 = (fact2 * fact3) % 1000000007;
		printf("%lld\n", (fact1 / fact2) % 1000000007);
	}

	return 0;
}