import sys
read=sys.stdin.buffer.read
readline=sys.stdin.buffer.readline
readlines=sys.stdin.buffer.readlines

MOD=10**9+7
MAX=10**6
f=[1]*(MAX+1)
invf=[1]*(MAX+1)
for i in range(2, MAX+1):
    f[i]=f[i-1]*i%MOD
invf[MAX]=pow(f[MAX], MOD-2, MOD)
for i in range(MAX-1, -1, -1):
    invf[i]=invf[i+1]*(i+1)%MOD
def comb(x, y):
    if not (0<=y and y<=x):
        return 0
    return f[x]*invf[y]*invf[x-y]%MOD
m=int(readline())
h=list(map(int, readline().split()))
if h[0]==0:
    print(1)
    exit()
k=len(h)
s=sum(h)
ans=comb(m-s+1, k)
if ans==0:
    print("NA")
else:
    print(ans)