n=int(input())
M=10**9+7

fa=[1,1]
fb=[1,1]
for i in range(2,n*2+1):
  fa+=[fa[-1]*i%M]
  fb+=[fb[-1]*(M//i)*fb[M%i]*fa[M%i-1]*(-1)%M]
c=lambda n,k:fa[n]*fb[k]*fb[n-k]%M if n>=k>=0 else "NA"

h=list(map(int,input().split()))
if h==[0]:
  print(1)
  exit()
k=len(h)
print(c(n-sum(h)-(k-1)+k+1-1,k+1-1))