mod = 998244353

n = int(input())
c = list(map(int, input().split()))

ans = 0
if 0 <= c[0] and 0 <= c[-1]:
    ans = pow(2, n-1, mod)
elif c[0] < 0 and c[-1] <= 0:
    ans = pow(2, n-1, mod)
elif 0 in c:
    ans = (pow(2, n-2, mod) * 3 % mod)
else:
    ans = pow(2, n-1, mod)

print(ans)