#include<bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
struct CombinationMod
{
  long long mod, size;
  vector< long long > fact;
  vector< long long > inv;
 
  void make_fact()
  {
    fact[0] = 1;
    for(int  i = 1; i < size; i++){
      fact[i] = fact[i-1] * i % mod;
    }
  }
 
  void make_inv()
  {
    inv[0] = inv[1] = 1;
    for(int i = 2; i < size; i++){
      inv[i] = inv[mod % i] * (mod - mod / i) % mod;
    }
    for(int i = 2; i < size; i++){
      inv[i] = inv[i-1] * inv[i] % mod;
    }
  }
  
  CombinationMod(int mod, int size = 10000000) : mod(mod), size(size+1)
  {
    fact.resize(size);
    inv.resize(size);
    make_fact();
    make_inv();
  }
  long long nCr(long long n, long long k)
  {
    if(k==0 || n==k) return 1;
    long long ret = fact[n] * inv[k] % mod * inv[n-k] % mod;
    return ret;
  }
};

int M, K;
int H[10000000];
int main()
{
  scanf("%d", &M);
  while(~scanf("%d", &H[K])) ++K;
  long long ALL = accumulate(H, H + K, 0LL);
  CombinationMod c(MOD);
  if(K == 1 && H[K] == 0) cout << 1 << endl;
  else if(M - ALL + 1 < K) cout << "NA" << endl;
  else cout << c.nCr(M - ALL + 1, K) << endl;
}