M=int(input())
H=list(map(int,input().split()))

mod=10**9+7

FACT=[1]
for i in range(1,2*10**6+1):
    FACT.append(FACT[-1]*i%mod)

FACT_INV=[pow(FACT[-1],mod-2,mod)]
for i in range(2*10**6,0,-1):
    FACT_INV.append(FACT_INV[-1]*i%mod)

FACT_INV.reverse()

def Combi(a,b):
    if 0<=b<=a:
        return FACT[a]*FACT_INV[b]%mod*FACT_INV[a-b]%mod
    else:
        return 0

x=sum(H)+len(H)-1
rest=M-x

if rest<0:
    print("NA")
else:
    print(Combi(rest+len(H),rest))