#yuki_389
import sys

mod=10**9+7
n=10**6
fact=[0 for i in xrange(n+1)]
inv=[0 for i in xrange(n+1)]
factr=[0 for i in xrange(n+1)]
inv[1]=fact[0]=factr[0]=1
for i in xrange(2,n+1):
 inv[i]=inv[mod%i]*(mod-mod/i)%mod
for i in xrange(1,n+1):
 fact[i]=fact[i-1]*i%mod
 factr[i]=factr[i-1]*inv[i]%mod

def comb(n,k):
 if k<0 or k>n: return 0
 return factr[k]*fact[n]%mod*factr[n-k]%mod
def perm(n,k):
 if k<0 or k>n: return 0
 return fact[n]*factr[n-k]%mod
def hcomb(n,k):
 if n==0 and k==0: return 1
 return comb(n+k-1,k)
 
m=int(raw_input())
h=map(int,raw_input().split())
if h[0]==0:
 print 1
 sys.exit()
if m-sum(h)-len(h)+1<0:
 print "NA"
 sys.exit()
k=len(h)
print hcomb(k+1,m-sum(h)-(k-1))