def modpow(s,q,mod):
    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())

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

if a[0] == 0:
	print 1
elif x < len(a)+len(a)-1:
	print "NA"
else:
	b = len(a)+1
	c = x-len(a)-len(a)+1
	d = 1
	for i in xrange(b,b+c):
		d *= i
		d %= 1000000007
	for i in xrange(1,c+1):
		d *= modpow(i,1000000005,1000000007)
		d %= 1000000007
	print d