N = int(input())
A = list(map(int, input().split()))
A = A + [A[0]]
for i in range(N):
    if A[i] == A[i + 1] == 1:
        print(0)
        exit()
        
A.pop()
cnt = A.count(1)
mod = 998244353
print(cnt * pow(N, mod - 2, mod) % mod)