#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
//#include<cctype>
#include<climits>
#include<iostream>
#include<string>
#include<vector>
#include<map>
//#include<list>
#include<queue>
#include<deque>
#include<algorithm>
//#include<numeric>
#include<utility>
//#include<memory>
#include<functional>
#include<cassert>
#include<set>
#include<stack>
#include<random>

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, -1, 0, 1};
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;


ll mod_pow(ll x, ll p, ll MOD) {
    ll a = 1;
    while (p) {
        if (p%2) a = a*x%MOD;
        x = x*x%MOD;
        p/=2;
    }
    return a;
}

// mod_inverse
ll mod_inverse(ll a, ll m) {
    return mod_pow(a, m-2, m);
}

const int MAXM = 1001000;
const int MOD = 1e9+7;
int H[MAXM];
ll fact[2*MAXM], rfact[2*MAXM];
int M, K;

ll nCr(int n, int r) {
    ll ret = fact[n];
    (ret *= rfact[r]) %= MOD;
    (ret *= rfact[n-r]) %= MOD;
    return ret;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    fact[0] = rfact[0] = 1;
    for (int i = 1; i < 2*MAXM; i++) {
        fact[i] = (fact[i-1]*i)%MOD;
        rfact[i] = mod_inverse(fact[i], MOD);
    }
    cin >> M;
    int sum = 0;
    while (cin >> H[K]) {
        sum += H[K++];
    }
    int rest = M-sum;
    rest -= K-1;
    if (rest < 0) {
        cout << "NA" << endl;
        return 0;
    }
    if (K == 1 && H[0] == 0) {
        cout << 1 << endl;
        return 0;
    }
    cout << nCr(rest+K, K) << endl;
    return 0;
}