#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <algorithm>
#include <sstream>
#include <cmath>
#include <set>
#include <iomanip>
#include <deque>
#include <list>
#include <stdio.h>
using namespace std;

#define REP(i,n) for(long long (i)=0;(i)<(long long)(n);(i)++)
#define RREP(i,n) for(long long (i)=(long long)(n)-1;i>=0;i--)
#define REMOVE(Itr,n) (Itr).erase(remove((Itr).begin(),(Itr).end(),n),(Itr).end())
#define UNIQUE(Itr) sort((Itr).begin(),(Itr).end()); (Itr).erase(unique((Itr).begin(),(Itr).end()),(Itr).end())

typedef long long ll;

#define MOD 1000000007

ll extgcd(ll a, ll b, ll& x, ll& y) {
    if(b==0){
        x=(a>=0)?1:-1;
        y=0;
        return abs(a);
    }else{
        ll res=extgcd(b,a%b,y,x);
        y-=(a/b)*x;
        return res;
    }
}

ll mod_inverse(ll a, ll m) {
    ll x,y;
    extgcd(a,m,x,y);
    return (m+x%m)%m;
}

ll c(ll n, ll k) {
    ll res=1;
    for(int i=0;i<k;i++)res=(res*((n-i)%MOD))%MOD;
    for(int i=1;i<=k;i++)res=(res*mod_inverse(i,MOD))%MOD;
    return res;
}

int main(){
    
    int N; cin>>N;
    vector<int> num;
    int t;
    while(cin>>t)num.push_back(t);
   if(num[0]==0){
cout<<1<<endl;
return 0;   
}    

    ll sum=0;
    REP(i,num.size())sum+=num[i]+1;
    sum--;
    if(sum==N){
        cout<<1<<endl;
        return 0;
    }else if(sum>N){
        cout<<"NA"<<endl;
        return 0;
    }
    
    ll x=N-sum;
    cout<<c(num.size()+x,x)<<endl;
    
    return 0;
}