#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>

using namespace std;
using ull = unsigned long long;
using ll = long long;
using lli = long long int;
using ld = long double;
using pa = pair<int,int>;
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define GRESORT(v) sort(v.begin(),v.end(),greater<int>())
#define REVERSE(v) reverse(v.begin(),v.end())
#define overlap(v) v.erase(unique(v.begin(),v.end()),v.end())
#define debug(x) cout << #x << ": " << x << endl
#define FOR(i,a,b) for(int i = (a); i < (b); i++)
#define rep(i,n) FOR(i,0,n)
#define RFOR(i,a,b) for(int i = (b-1); i >= a; i--)
#define rrep(i,n) RFOR(i,0,n)
#define INF 999999999
#define mins(a,b) a = min(a,b);
#define maxs(a,b) a = max(a,b);

//4近傍
//int dy[]={0, 0, 1, -1};
//int dx[]={1, -1, 0, 0};

//8近傍
//int dy[]={0,0,1,-1,1,1,-1,-1};
//int dx[]={1,-1,0,0,1,-1,1,-1};

ll mod = 1000000007;
vector<ll> fact;

ll pow_mod(ll a,ll b){
    ll ret = 1;
    while(b > 0){
        if(b & 1){
            ret = ret * a % mod;
        }
        a = a * a % mod;
        b >>= 1;
    }
    return ret;
}

ll comb(ll x,ll y){
    return fact[x] * pow_mod(fact[y] * fact[x-y] % mod,mod-2) % mod;
}

void solve(){
    int m; cin >> m;
    fact.resize(m);
    fact[0] = 1;
    fact[1] = 1;
    for(ll i = 2; i < m; i++){
        fact[i] = fact[i-1] * i % mod;
    }
    ll sum = 0, cnt = 0;
    ll val;
    while(cin >> val){
        if(val == -1) break;
        sum += val;
        cnt++;
    }
    if(sum + cnt - 1 > m){
        cout << "NA" << endl;
        return;
    }
    if(sum == 0){
        cout << 1 << endl;
        return;
    }

    ll ans = comb(m - sum + 1,cnt);
    ans = (ans+mod) % mod;
    cout << ans << endl;
}

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    solve();

    return 0;
}