#include <cstdio>
#include <iostream>
#include <algorithm>
using namespace std;
typedef long long ll;
#define mod 1000000007

ll mf[1111111];
ll fact(ll n){
  if(mf[n]) return mf[n];

  ll ret = 1;
  for(ll i = 1; i <= n; i++){
    ret *= i;
    ret %= mod;
  }
  return mf[n] = ret;
}
ll inv(ll x,ll m){
  ll ret = 1;
  ll k = x;
  for(ll i = m-2; i > 0; i>>=1){
    if(i&1){
      ret *= k;
      ret %= m;
    }
    k *= k;
    k %= m;
  }
  return ret;
}

int m;
int k;
int H[1111111];
int main(void){
  scanf("%d",&m);
  int sum = 0;
  for(k = 0; scanf("%d",H+k)!=EOF; k++) sum += H[k];

  if(sum == 0 || sum+k-1 > m){
    puts("NA");
  }else{
    ll ans = 0;

    /*
    for(ll i = 0; i <= m-(sum+k-1); i++){
      ans +=  fact(i+k-1)*inv(fact(i)*fact(k-1)%mod,mod)%mod;
      ans %= mod;
      printf("%lld\n",i);
    }
    */
    ll x = m-(sum+k-1);
    ans += fact(x+k)*inv(fact(x)*fact(k)%mod,mod)%mod;
    ans %= mod;
    
    printf("%lld\n",ans);
  }
    
}