import sys

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = 10**16
md = 998244353
# md = 10**9+7

from collections import defaultdict

n = II()
aa = LI()

dp = defaultdict(int)
c2 = 0
s = 1
dp[c2, s] = 1
two = 1

ans = 0
for i, a in enumerate(aa):
    if a==0:
        dp = defaultdict(int)
        c2 = 0
        s = 1
        dp[c2, s] = 1
        two = 2
    else:
        if abs(a) == 2: c2 += 1
        if a < 0: s *= -1
        dp[c2, s] += two
        if i < n-1: two = two*2%md
        ans += dp[c2-1, -s]*pow(two, md-2, md)%md
        ans %= md
        # print(ans, dp)

print(ans)