mod = 1000000007

def modpow(s,q):
    ret = 1
    while q > 0:
        if q % 2 == 1: 
            ret = (s * ret) % mod
        s = (s * s) % mod; q = q/2
    return ret

x = input()
a = map(int,raw_input().split())
l = len(a)

for i in xrange(l):
	x = x - a[i] + 1

if a[0] == 0:
	print 1
elif x < l*2-1:
	print "NA"
else:
	d = 1
	for i in xrange(l+1,x-l+2):
		d *= i*modpow(i-l,mod-2)
		d %= mod
	print d