#include<iostream>
using namespace std;
long mod=1e9+7;
long power(long a,long b){return b?power(a*a%mod,b/2)*(b%2?a:1)%mod:1;}
main()
{
	int M;cin>>M;
	int s=0,c=0;
	for(int h;cin>>h;c++)s+=h;
	if(s==0)c=0;
	if(s+c-1>M)
	{
		cout<<"NA"<<endl;
		return 0;
	}
	long a=1,b=1;
	int N=c+1,K=M-(s+c-1);
	N+=K-1;
	for(long i=1;i<=K;i++)
	{
		a=a*(N-i+1)%mod;
		b=b*i%mod;
	}
	cout<<a*power(b,mod-2)%mod<<endl;
}