#!/usr/bin/env python
#coding:utf8

MOD = 1000000007


def read():
    M = input()
    hList = map(int, raw_input().split())
    return M, hList


def mypow(p, n):
    if n == 0:
        return 1
    t = mypow(p, n / 2)
    return t * t % MOD if n % 2 == 0 else t * t * p % MOD
    

def nCk(n, k):
    nume = 1
    for i in range(k):
        nume = nume * (n - i) % MOD
    
    deno = 1
    for i in range(k):
        deno = deno * (i + 1) % MOD
    
    return nume * mypow(deno, MOD - 2) % MOD


def nHk(n, k):
    return nCk(n + k - 1, k)


def work((M, hList)):
    if sum(hList) == 0:
        print 1
        return
    
    N = len(hList) + 1
    K = M - sum(hList) - (len(hList) - 1)
    
    if K < 0:
        print "NA"
    else:
        print nHk(N, K)


if __name__ == "__main__":
    work(read())