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

#define _p(...) (void)printf(__VA_ARGS__)
#define forr(x,arr) for(auto&& x:arr)
#define _overload3(_1,_2,_3,name,...) name
#define _rep2(i,n) _rep3(i,0,n)
#define _rep3(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,_rep3,_rep2,)(__VA_ARGS__)
#define _rrep2(i,n) _rrep3(i,0,n)
#define _rrep3(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define rrep(...) _overload3(__VA_ARGS__,_rrep3,_rrep2,)(__VA_ARGS__)
#define ALL(x) (x).begin(), (x).end()
#define BIT(n) (1LL<<(n))
#define SZ(x) ((int)(x).size())
#define fst first
#define snd second
typedef vector<int> vi;typedef vector<vi> vvi;typedef pair<int,int> pii;typedef vector<pii> vpii;
typedef long long ll;

const long long mod = 1000000007;

long long powMod(long long x, long long y) {
  long long r = 1, a = x % mod;
  while (y) {
    if (y & 1) r = (r * a) % mod;
    a = a * a % mod;
    y /= 2;
  }
  return r;
}

long long getC(int a, int b) {
  long long ans = 1;
  if (b > a / 2) return getC(a, a - b);
  long long div = 1;
  for (int i = 0; i < b; i++) {
    ans *= a - i;
    ans %= mod;
    div *= i + 1;
    div %= mod;
  }
  ans *= powMod(div, mod - 2);
  return ans % mod;
}

void Main() {
  ll X;
  cin >> X;
  vi H;
  int x;
  while (cin >> x) {
    H.push_back(x);
  }

  if (SZ(H) == 1 && H[0] == 0) {
    cout << "1" << endl;
    return;
  }

  ll must = accumulate(ALL(H), 0) + SZ(H) - 1;

  int N = X - must;
  int M = SZ(H) + 1;

  if (N < 0) {
    cout << "NA" << endl;
    return;
  }

  ll ans = getC(N+M-1, M-1);
  cout << ans << endl;
}
int main() { cin.tie(0); ios::sync_with_stdio(false); Main(); return 0; }