#include<bits/stdc++.h> using namespace std; #define rep(i,a,b) for(int i=a;i<b;i++) typedef long long ll; ll mo = 1000000007; //----------------------------------------------------------------- ll combi(ll N_, ll C_) { const int NUM_ = 2000001; static ll fact[NUM_ + 1], factr[NUM_ + 1], inv[NUM_ + 1]; if (fact[0] == 0) { inv[1] = fact[0] = factr[0] = 1; for (int i = 2; i <= NUM_; ++i) inv[i] = inv[mo % i] * (mo - mo / i) % mo; for (int i = 1; i <= NUM_; ++i) fact[i] = fact[i - 1] * i%mo, factr[i] = factr[i - 1] * inv[i] % mo; } if (C_<0 || C_>N_) return 0; return factr[C_] * fact[N_] % mo*factr[N_ - C_] % mo; } //----------------------------------------------------------------- ll nHk(ll n, ll k) { return combi(n + k - 1, k - 1); } //----------------------------------------------------------------- int M; vector<int> H; //----------------------------------------------------------------- int main() { cin >> M; int x; while(cin >> x) H.push_back(x); if (H.size() == 1 && H[0] == 0) { printf("1\n"); return 0; } int sum = 0; rep(i, 0, H.size()) sum += H[i]; int a = M - sum - (H.size() - 1); int b = H.size() + 1; if (a < 0) { cout << "NA" << endl; return 0; } //cout << a << endl; //cout << b << endl; ll ans = nHk(a, b); cout << ans << endl; }