N = int(input())
C = list(map(int, input().split()))

MOD = 998244353

if 0 <= C[0] and 0 <= C[-1]:
    print(pow(2, N-1, MOD))
elif C[0] < 0 and C[-1] < 0:
    print(pow(2, N-1, MOD))
elif 0 in C:
    print(pow(2, N-2, MOD)*3)
else:
    print(pow(2, N-1, MOD))