#define P 1000000007
long v[1<<20],s;n,k,i,t;
main(j){
	for(v[1]=s=scanf("%d",&n);j++<1e6;v[j]=v[P%j]*(P-P/j)%P);
	for(;~scanf("%d",&t);k+=!!t)n-=t;
	for(;k/++i;)s=s*(n-i+2)%P*v[i]%P;
	s=!printf(s?"%ld":"NA",s);
}