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 LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
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 = 18446744073709551615
inf = 4294967295
# md = 10**9+7
md = 998244353

def nCr(n, r):
    n ^= mask
    if n & r: return 0
    return 1

mask = (1 << 18)-1
n = II()
bb = LI()
cc = []
for i in range(n):
    cc.append(nCr(n-1, i))
# print(cc)

cnt = [0, 0]
for b, c in zip(bb, cc):
    if b == -1: cnt[c] += 1

if cnt[1] == 0:
    x = 0
    for b, c in zip(bb, cc):
        if b == -1: continue
        x ^= b*c
    if x == 1: ans = pow(2, cnt[0], md)
    else: ans = 0

else:
    ans = pow(2, cnt[0]+cnt[1]-1, md)

print(ans)