#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X))
#define reps(X,S,Y) for (int (X) = S;(X) < (Y);++(X))
#define rrep(X,Y) for (int (X) = (Y)-1;(X) >=0;--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<class T> using vv=vector<vector<T>>;
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
os<<"{"; rep(i,t.size()) {os<<t[i]<<",";} os<<"}"<<endl; return os;}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
const ll MOD=1e9+7;
vector<ll> fact,finv,inv;
ll comb(ll n,ll r){
  if(n<r||r<0)return 0;
  return fact[n]*finv[n-r]%MOD*finv[r]%MOD;
}
class Doralion{
  void Modinvs(vector<ll> &re,int n){
    re.resize(n+1); re[1]=1;
    for(int i=2;i<=n;++i)re[i]=re[MOD%i]*(MOD-MOD/i)%MOD;
  }
  void Facts(vector<ll> &re,int n){
    re.resize(n+1); re[0]=1;
    rep(i,n)re[i+1]=re[i]*(i+1)%MOD;
  }
  void Factinvs(vector<ll> &re,const vector<ll> &inv,int n){
    re.resize(n+1); re[0]=1;
    rep(i,n)re[i+1]=re[i]*inv[i+1]%MOD;
  }
public:
  Doralion(int n){
    Modinvs(inv,n);
    Facts(fact,n);
    Factinvs(finv,inv,n);
  }
} doralion(2123456);

int main(){
  ios_base::sync_with_stdio(false);
  cout<<fixed<<setprecision(0);
  int m;
  cin>>m;
  vector<int> a;
  int x;
  while(cin>>x) a.pb(x);
  if(a[0]==0){
    cout<<1<<endl;
    return 0;
  }
  int n=a.size();
  int s=accumulate(all(a),-n);
  m-=s;
  if(m<n*2-1){
    cout<<"NA"<<endl;
    return 0;
  }
  cout<<comb(m-n+1,n)<<endl;
  return 0;
}