import sys
#input = sys.stdin.readline
input = sys.stdin.buffer.readline

def cmb(n,k):
    if (k<0) or (n<k): return 0
    ret = 1
    for i in range(2,n+1):
        ret *= i
    for i in range(2,k+1):
        ret //= i
    for i in range(2,(n-k)+1):
        ret //= i
    return ret

def lucas(n,k,p):
    keta = 1
    m = n
    while m > 0:
        keta += 1
        m //= p

    ret = 1    
    for i in range(keta):
        nn = n>>i
        kk = k>>i
        temp = cmb(nn,kk)%p
        ret = ret*temp%p
    return ret
        


def main():
    n = int(input()); MOD = 998244353
    B = list(map(int,input().split()))

    #dp[i][j]:i番目まで見て和が0(偶数)/1(奇数)
    dp = [1,0]
    for i in range(n):
        p = [0,0]
        p,dp = dp,p
        pari = lucas(n-1,i,2)
        if B[i] == 0:
            dp[0] = p[0]
            dp[1] = p[1]
        elif B[i] == 1:
            if pari == 0:
                dp[0] = p[0]
                dp[1] = p[1]
            else:
                dp[0] = p[1]
                dp[1] = p[0]
        else:
            if pari == 0:
                dp[0] = 2*p[0]
                dp[1] = 2*p[1]
            else:
                dp[0] = p[0] + p[1]
                dp[1] = p[0] + p[1]
        dp[0] %= MOD
        dp[1] %= MOD

    ans = dp[1]
    print(ans%MOD)



if __name__ == '__main__':
    main()