#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef pair< int, int > pii;
typedef vector< pii > vp;
typedef vector< double > vd;
typedef vector< vd > vvd;
typedef vector< string > vs;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

const int INF = 0x3f3f3f3f;
const int MOD7 = ( int ) 1e9 + 7;

int M;
vi H;

void init(){
  cin >> M;
  int h;
  while( cin >> h )
    if( h )
      H.emplace_back( h );
}

int n, m;
int sum_h;

int int_pow( int v, int p ){
  int res = v != 0 or p == 0;
  while( p ){
    if( p & 1 )
      res = 1LL * res * v % MOD7;
    p >>= 1;
    v = 1LL * v * v % MOD7;
  }
  return res; 
}

int mod_inv( int v ){
  return int_pow( v, MOD7 - 2 );
}

int comb( int n, int m ){
  int res = 1;
  for( int i = 2; i <= n; ++i )
    res = 1LL * res * i % MOD7;
  for( int i = 2; i <= m; ++i )
    res = 1LL * res * mod_inv( i ) % MOD7;
  for( int i = 2; i <= n - m; ++i )
    res = 1LL * res * mod_inv( i ) % MOD7;
  return res;
}

void preprocess(){
  for( int i = 0; i < H.size(); ++i )
    sum_h += H[ i ];
  n = M - ( sum_h + H.size() - 1 ); // number of free balls
  m = H.size() + 1; // number of choices to put free balls
  if( n < 0 )
    cout << "NA" << endl, exit( 0 );
}

void solve(){
  cout << comb( m + n - 1, n ) << endl;
}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}