#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <list>
#include <vector>
#include <complex>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <bitset>
#include <ctime>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <cassert>
#include <cstddef>
#include <iomanip>
#include <numeric>
#include <tuple>
#include <sstream>
#include <fstream>

#define REP(i,n) for(long (i)=0;(i)<(n);(i)++)
#define FOR(i,a,b) for(long (i)=(a);(i)<(b);(i)++)
#define RREP(i,a) for(long (i)=(a)-1;(i)>=0;(i)--)
#define FORR(i,a,b) for(long (i)=(a)-1;(i)>=(b);(i)--)
#define PI acos(-1.0)
#define DEBUG(C) cout<<C<<endl;
#define VI vector<int>
#define VL vector<long>
#define VD vector<double>
#define PII pair<int,int>
#define PDD pair<double,double>
#define PLL pair<long,long>
#define ALL(a) (a).begin(),(a).end()
#define SORT(a) sort(ALL(a))
#define REVERSE(a) reverse(ALL(a))
#define MP make_pair
#define FORE(a,b) for(auto &&a:b)

using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
const int INF=1e9;
const int MOD=INF+7;

LL pow_mod(LL a,LL p){
    if(p==0) return 1;
    if(p&1) return a*pow_mod(a,p-1)%MOD;
    LL t=pow_mod(a,p/2);
    return t*t%MOD;
}

LL fact_mod(LL n){
    LL ret=1;
    for(LL i=n;i>1;i--){
        ret*=i; ret%=MOD;
    }
    return ret;
}

LL fact_mod_inverse(LL n){
    if(n==1) return 1;
    LL t=fact_mod(n);
    return pow_mod(t,MOD-2)%MOD;
}

int main(void){
    int M; cin>>M;
    vector<int> H;
    int buf; long sum=0;
    while(cin>>buf){
        H.emplace_back(buf);
        sum+=buf;
    }
    if(H[0]==0&&H.size()==1){
        cout<<1<<endl;
        return 0;
    }
    if(M<sum+H.size()-1){
        cout<<"NA"<<endl;
        return 0;
    }
    LL ans=fact_mod(M-sum+1);
    ans*=fact_mod_inverse(M-sum+1-H.size()); ans%=MOD;
    ans*=fact_mod_inverse(H.size()); ans%=MOD;
    cout<<ans<<endl;
    return 0;
}