#include <iostream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <cassert>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <string>
#include <algorithm>
#include <utility>
#define llint long long
#define inf 1e18
#define rep(x, s, t) for(llint (x) = (s); (x) < (t); (x)++)
#define Rep(x, s, t) for(llint (x) = (s); (x) <= (t); (x)++)
#define chmin(x, y) (x) = min((x), (y))
#define chmax(x, y) (x) = max((x), (y))
#define mod 998244353

using namespace std;
typedef pair<llint, llint> P;

llint n;
llint a[200005];

llint calc(llint p)
{
	llint sum[2] = {0, 0}, parity = 0, mul = (mod+1)/2;
	if(p == n) mul = 1;
	sum[0] += mul, sum[0] %= mod;
	
	for(int i = 1; ; i++){
		if(p+i > n || abs(a[p+i]) != 1) break;
		if(a[p+i] < 0) parity ^= 1;
		if(p+i < n) mul *= (mod+1)/2, mul %= mod;
		sum[parity] += mul, sum[parity] %= mod;
	}
	
	llint sum2[2] = {0, 0};
	parity = 0, mul = (mod+1)/2;
	if(p == 1) mul = 1;
	sum2[0] += mul, sum2[0] %= mod;
	
	for(int i = 1; ; i++){
		if(p-i <= 0 || abs(a[p-i]) != 1) break;
		if(a[p-i] < 0) parity ^= 1;
		if(p-i > 1) mul *= (mod+1)/2, mul %= mod;
		sum2[parity] += mul, sum2[parity] %= mod;
	}
	
	llint ret;
	if(a[p] > 0) ret = (sum[0]*sum2[1]%mod + sum[1]*sum2[0]%mod) % mod;
	else ret = (sum[0]*sum2[0]%mod + sum[1]*sum2[1]%mod) % mod;
	return ret;
}

int main(void)
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n;
	for(int i = 1; i <= n; i++) cin >> a[i];
	
	llint ans = 0;
	for(int i = 1; i <= n; i++){
		if(abs(a[i]) == 2) ans += calc(i), ans %= mod;
	}
	cout << ans << endl;
	
	return 0;
}