// yukicoder: No.389 ロジックパズルの組み合わせ
// 2019.7.14 bal4u

#include <stdio.h>

typedef long long ll;

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int eol;
int in() {   // 非負整数の入力
	int n, c;

	if (eol) return -1;
	n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	if (c < ' ') eol = 1;
	return n;
}

#define MOD 1000000007
#define MAX 500000
int fact[MAX+2] = {1,1};
int inv[MAX+2] = {1,1};
int invfact[MAX+2] = {1,1};

int main()
{
	int i, h, s, k, M;
	ll ans;
	
	M = in(); eol = 0;
	s = k = 0; while ((h = in()) >= 0) s += h, k++;
	if (s+k-1 > M) { puts("NA"); return 0; }
	else if (s == 0 || s+k-1 == M) ans = 1;
	else {
		for (i = 2; i <= k; i++) {
			fact[i] = (ll)fact[i-1]*i % MOD;
			inv[i] = -(MOD/i)*(ll)inv[MOD % i] % MOD;
			invfact[i] = (ll)invfact[i-1]*inv[i] % MOD;
		}
		ans = invfact[k];
		h = M-s-k+1; for (i = 1; i <= k; i++) ans = ans * (h+i) % MOD;
		if (ans < 0) ans += MOD;
	}
	printf("%d\n", (int)ans);
	return 0;
}