class Combi():
    def __init__(self, N, mod):
        self.power = [1 for _ in range(N+1)]
        self.rev = [1 for _ in range(N+1)]
        self.mod = mod
        for i in range(2, N+1):
            self.power[i] = (self.power[i-1]*i) % self.mod
        self.rev[N] = pow(self.power[N], self.mod-2, self.mod)
        for j in range(N, 0, -1):
            self.rev[j-1] = (self.rev[j]*j) % self.mod

    def C(self, K, R):
        if K < R:
            return "NA"
        else:
            return ((self.power[K])*(self.rev[K-R])*(self.rev[R])) % self.mod

    def P(self, K, R):
        if K < R:
            return "NA"
        else:
            return (self.power[K])*(self.rev[K-R]) % self.mod

mod =10**9 + 7
M = int(input())
H = list(map(int, input().split()))
L = len(H)
M += (L-sum(H))
M -= (L-1)
if M >= 0:
    c = Combi(M, mod)
    print(c.C(M, L))
else:
    print("NA")