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))