import sys
input = sys.stdin.readline
def main():
    N=int(input())
    assert(1<=N<=200000)
    A=list(map(int,input().split()))
    for x in A:
        assert(abs(x)<=2)
    MOD=998244353
    dp=[[[0 for _ in range(3)] for _ in range(3)] for _ in range(2)]
    dp2=[[[0 for _ in range(3)] for _ in range(3)] for _ in range(2)]
    dp[0][0][0]=1
    for i in range(N):
        neg=(1 if A[i]<0 else 0)
        two=(2 if A[i]==0 else (1 if abs(A[i])==2 else 0))
        
        for j in range(2):
            for k in range(3):
                if i==0:
                    dp2[j][k][0]+=dp[j][k][0]
                else:
                    dp2[j][k][0]+=2*dp[j][k][0]
                dp2[(j+neg)%2][min(2,k+two)][1]+=dp[j][k][1]+dp[j][k][0]
                dp2[(j+neg)%2][min(2,k+two)][2]+=dp[j][k][1]+dp[j][k][0]
                if i==N-1:
                    dp2[j][k][2]+=dp[j][k][2]
                else:
                    dp2[j][k][2]+=2*dp[j][k][2]
        for j in range(2):
            for k in range(3):
                for l in range(3):
                    dp[j][k][l]=dp2[j][k][l]%MOD
                    dp2[j][k][l]=0
    ans=dp[1][1][2]
    print((ans*pow(pow(2,N-1,MOD),MOD-2,MOD))%MOD)
if __name__=='__main__':
    main()