#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cstring>
#include <complex>
#include <stack>
#include <queue>
#include <unordered_map>
#include <map>

//#define INF 100000000
//#define MOD (int) (1e9+7)
#define rep(i, a) for (int i = 0; i < (a); i++)
using namespace std;

const int MAX = 1000000;
const int MOD = 1000000007;

long long fac[MAX], finv[MAX], inv[MAX];

void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        //そのまま計算すると負の値になるのでMODを足す
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

// 二項係数計算
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

int main(){
    int m;
    cin >> m;

    vector<int> v;
    int h;
    int sum = 0;
    while(cin >> h){
        sum += h;
        v.push_back(h);
    }

    if(sum + v.size() - 1 > m){
        cout << "NA" << endl;
        return 0;
    }

    if(sum == 0){
        cout << 1 << endl;
        return 0;
    }

    COMinit();
    cout << COM(m-sum+1, m-sum-v.size()+1) << endl;
}