m=998244353
b=1
q=1
r='m+1>>1'
read a
read a
for a in $a;{((
	b+=q, b-=b<m?0:m,
	q+=q, q-=q<m?0:m,
	r=r*(m+1>>1)%m,
	a || (b=c=d=e=0),
	a<0 && (t=b,b=c,c=t,t=d,d=e,e=t),
	(a&3)==2 && (d=b,e=c,b=c=0),
	z=(z+e*r)%m
));}
echo $[(z+e*r)%m]