#![allow(non_snake_case, unused_imports, unused_must_use)]
use std::io::{self, prelude::*};
use std::str;

const MOD: usize = 998_244_353;

fn main() {
    let (stdin, stdout) = (io::stdin(), io::stdout());
    let mut scan = Scanner::new(stdin.lock());
    let mut out = io::BufWriter::new(stdout.lock());

    macro_rules! input {
        ($T: ty) => {
            scan.token::<$T>()
        };
        ($T: ty, $N: expr) => {
            (0..$N).map(|_| scan.token::<$T>()).collect::<Vec<_>>()
        };
    }

    let N = input!(usize);
    let S = input!(String).chars().collect::<Vec<_>>();

    let mut dp = vec![vec![0; 2]; N + 1];
    dp[0][0] = 1;

    for i in 0..N {
        let s = S[i];

        match s {
            '1' => {
                dp[i + 1][1] += dp[i][1] * 2;
                dp[i + 1][1] += dp[i][0];

                dp[i + 1][1] %= MOD;
            }
            '0' => {
                dp[i + 1][0] += dp[i][0];
                dp[i + 1][1] += dp[i][1];
                dp[i + 1][0] += dp[i][1];

                dp[i + 1][0] %= MOD;
                dp[i + 1][1] %= MOD;
            }
            _ => {
                unreachable!();
            }
        }
    }

    writeln!(out, "{}", dp[N][1]);
}

struct Scanner<R> {
    reader: R,
    buf_str: Vec<u8>,
    buf_iter: str::SplitWhitespace<'static>,
}
impl<R: BufRead> Scanner<R> {
    fn new(reader: R) -> Self {
        Self {
            reader,
            buf_str: vec![],
            buf_iter: "".split_whitespace(),
        }
    }
    fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buf_iter.next() {
                return token.parse().ok().expect("Failed parse");
            }
            self.buf_str.clear();
            self.reader
                .read_until(b'\n', &mut self.buf_str)
                .expect("Failed read");
            self.buf_iter = unsafe {
                let slice = str::from_utf8_unchecked(&self.buf_str);
                std::mem::transmute(slice.split_whitespace())
            }
        }
    }
}