const OFFSET: usize = 2;
const MOD: usize = 998244353;

fn power(base: usize, times: usize) -> usize {
    if times == 0 { return 1usize; }
    if times == 1 { return base; }
    let temp = power(base, times/2);
    temp * temp % MOD * power(base, times%2) % MOD
}

fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: Vec<isize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut p2s = vec![1usize; n];
    for i in (1..n-1).rev() { p2s[i-1] = p2s[i] * 2 % MOD; }
    let mut dp = vec![vec![0usize; 6]; n+1];
    dp[0][OFFSET+1] = 1;
    let mut result = 0usize;
    for i in 0..n {
        for j in -2..=3 {
            let jidx = OFFSET as isize + j;
            let jidx = jidx as usize;
            if a[i].abs() * j.abs() > 2 {
                dp[i+1][5] += dp[i][jidx];
                dp[i+1][5] %= MOD;
                continue;
            }
            let njidx = OFFSET as isize + a[i] * j;
            let njidx = njidx as usize;
            dp[i+1][njidx] += dp[i][jidx];
            dp[i+1][njidx] %= MOD;
            if njidx == 0 {
                result += dp[i][jidx] * p2s[i];
                result %= MOD;
            }
        }
        if i == 0 { continue; }
        for j in -2..=3 {
            let jidx = OFFSET as isize + j;
            let jidx = jidx as usize;
            let njidx = OFFSET as isize + a[i];
            let njidx = njidx as usize;
            dp[i+1][njidx] += dp[i][jidx];
            dp[i+1][njidx] %= MOD;
            if njidx == 0 {
                result += dp[i][jidx] * p2s[i];
                result %= MOD;
            }
        }
    }
    println!("{}", result * power(power(2, MOD-2), n-1) % MOD);
}