import bisect
import copy
import decimal
import fractions
import heapq
import itertools
import math
import random
import sys
from collections import Counter,deque,defaultdict
from functools import lru_cache,reduce
from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max
def _heappush_max(heap,item):
    heap.append(item)
    heapq._siftdown_max(heap, 0, len(heap)-1)
def _heappushpop_max(heap, item):
    if heap and item < heap[0]:
        item, heap[0] = heap[0], item
        heapq._siftup_max(heap, 0)
    return item
from math import gcd as GCD, modf
read=sys.stdin.read
readline=sys.stdin.readline
readlines=sys.stdin.readlines

def Extended_Euclid(n,m):
    stack=[]
    while m:
        stack.append((n,m))
        n,m=m,n%m
    if n>=0:
        x,y=1,0
    else:
        x,y=-1,0
    for i in range(len(stack)-1,-1,-1):
        n,m=stack[i]
        x,y=y,x-(n//m)*y
    return x,y

class MOD:
    def __init__(self,mod):
        self.mod=mod
    
    def Pow(self,a,n):
        a%=self.mod
        if n>=0:
            return pow(a,n,self.mod)
        else:
            assert math.gcd(a,self.mod)==1
            x=Extended_Euclid(a,self.mod)[0]
            return pow(x,-n,self.mod)

    def Build_Fact(self,N):
        assert N>=0
        self.factorial=[1]
        for i in range(1,N+1):
            self.factorial.append((self.factorial[-1]*i)%self.mod)
        self.factorial_inv=[None]*(N+1)
        self.factorial_inv[-1]=self.Pow(self.factorial[-1],-1)
        for i in range(N-1,-1,-1):
            self.factorial_inv[i]=(self.factorial_inv[i+1]*(i+1))%self.mod
        return self.factorial_inv

    def Fact(self,N):
        return self.factorial[N]

    def Fact_Inv(self,N):
        return self.factorial_inv[N]

    def Comb(self,N,K):
        if K<0 or K>N:
            return 0
        s=self.factorial[N]
        s=(s*self.factorial_inv[K])%self.mod
        s=(s*self.factorial_inv[N-K])%self.mod
        return s

M,*H=map(int,read().split())
S=sum(H)+len(H)-1
if H==[0]:
    ans=1
elif S>M:
    ans='NA'
else:
    mod=10**9+7
    MD=MOD(mod)
    MD.Build_Fact(2*10**6)
    ans=MD.Comb(M-S+len(H),len(H))
print(ans)