#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b)*b; }
template<class S,class T> ostream& operator << (ostream& out,const pair<S,T>& o){ out << "(" << o.first << "," << o.second << ")"; return out; }
template<class T> ostream& operator << (ostream& out,const vector<T> V){ for(int i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; }
template<class T> ostream& operator << (ostream& out,const vector<vector<T> > Mat){ for(int i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out << Mat[i];} return out; }
template<class S,class T> ostream& operator << (ostream& out,const map<S,T> mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out << it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; }

/*
 <url:https://yukicoder.me/problems/no/389>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

const ll MOD = 1e9+7;
string solve(){
    string res;
    ll M; cin >> M;
    vector<ll> H;
    ll h;
    while(cin >> h){
        H.push_back(h);
    }
    if(H[0] == 0) return to_string(1);
    if(accumulate(H.begin(),H.end(),0LL)+H.size()-1 > M) return "NA";
    
    vector<vector<ll>> dp(M+3,vector<ll>(H.size()+1));
    dp[1][0] = 1;
    for(int i = 1; i <= M+1;i++){
        for(int j = 0; j < H.size();j++){
            if(dp[i][j] == 0) break;
            (dp[i+1][j] += dp[i][j])%=MOD;
            if(i+H[j]+1 <= M+2) (dp[i+H[j]+1][j+1] += dp[i][j])%=MOD;
        }
        (dp[i+1][H.size()] += dp[i][H.size()])%=MOD;
    }
    //cout << dp << endl;
    return res = to_string(dp[M+2][H.size()]);
}
int main(void) {
    cin.tie(0); ios_base::sync_with_stdio(false);
    cout << solve() << endl;
    return 0;
}