N = int(input())
A = [int(a) for a in input().split()]
P = 998244353
inv2 = (P + 1) // 2
X = [[0] * 6 for _ in range(N + 1)]
X[0][1] = 1
for i, a in enumerate(A):
    X[i+1][a] = (X[i+1][a] + inv2) % P
    for j in range(-2, 4):
        ne = 3 if (j == 3 or abs(j * a) > 2) else j * a
        X[i+1][ne] = (X[i+1][ne] + X[i][j] * inv2) % P

print(sum([x[-2] for x in X] + [X[-1][-2]]) * inv2 % P)