#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef int _loop_int;
#define REP(i,n) for(_loop_int i=0;i<(_loop_int)(n);++i)
#define FOR(i,a,b) for(_loop_int i=(_loop_int)(a);i<(_loop_int)(b);++i)
#define FORR(i,a,b) for(_loop_int i=(_loop_int)(b)-1;i>=(_loop_int)(a);--i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

// mod
const ll MOD = 1000000007ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

// floating
typedef double Real;
const Real EPS = 1e-11;
#define EQ0(x) (abs(x)<EPS)
#define EQ(a,b) (abs(a-b)<EPS)
typedef complex<Real> P;

int m;
int k;
int h[1252525];

ll fact[1252525];
void init(){
  fact[0] = 1;
  FOR(i,1,1252525){
    fact[i] = i*fact[i-1]%MOD;
  }
}

ll inv(ll x){
  ll k = MOD-2;
  ll ret = 1;
  while(k){
    if(k&1)ret=ret*x%MOD;
    x=x*x%MOD;
    k>>=1;
  }
  return ret;
}

int comb(int a,int b){
  ll ret = 1;
  init();
  ret *= fact[a];
  ret %= MOD;
  ret *= inv(fact[b]);
  ret %= MOD;
  ret *= inv(fact[a-b]);
  ret %= MOD;
  return (int)ret;
}

int main(){
  scanf("%d",&m);
  k=0;
  while(~scanf("%d",&h[k++]));
  --k;
  if(h[0]==0){
    puts("1");
    return 0;
  }
  int sum = 0;
  REP(i,k)sum += h[i];
  m -= sum;
  if(m+1<k){
    puts("NA");
    return 0;
  }
  // ans = m+1 C k
  printf("%d\n",comb(m+1,k));
  return 0;
}