#include <iostream>
#include <algorithm>
#include <tuple>
using namespace std;
using i64 = long long;

constexpr i64 mod = i64(powl(10, 9)) + 7;

tuple<i64, i64, i64> extgcd(i64 x, i64 y) {
  if(y == 0) { return make_tuple(1, 0, x); }
  i64 a, b, d; tie(a, b, d) = extgcd(y, x%y);
  return make_tuple(b, a-x/y*b, d);
}

i64 mod_inv(const i64 &a, const i64 &m) {
  i64 x, _, d; tie(x, _, d) = extgcd(a, m);
  if(d == 1) { return (x % m + m) % m; }
  throw;
}

i64 nCr(i64 n, i64 r, i64 mod) {
  vector<i64> fact(n+1, 1);
  for(i64 i=2; i<=n; ++i) {
    fact[i] = fact[i-1] * i;
    fact[i] %= mod;
  }
  i64 inv1 = mod_inv(fact[r],   mod),
      inv2 = mod_inv(fact[n-r], mod);
  i64 res = fact[n];
  res *= inv1;
  res %= mod;
  res *= inv2;
  res %= mod;
  return res;
}

int main(void) {
  i64 m; scanf("%lld", &m);
  vector<i64> a;
  for(i64 x; ~scanf("%lld", &x); a.push_back(x)) ;
  i64 n = a.size();
  i64 acc = accumulate(begin(a), end(a), 0);
  if(a[0] == 0) {
    puts("1");
    return 0;
  }
  if(acc + n - 1 > m) {
    puts("NA");
    return 0;
  }
  i64 res = nCr(m-acc+1, n, mod);
  printf("%lld\n", res);
  return 0;
}