#include <bits/stdc++.h>
using namespace std;

#define MOD 998244353

long long modpow(long long a, long long n, long long mod) {
	long long res = 1;
	while (n > 0) {
		if (n & 1) res = res * a % mod;
		a = a * a % mod;
		n >>= 1;
	}
	return res;
}

int main() {
	long long N; cin >> N;
	string S; cin >> S;

	vector<vector<long long>> dp1(N, vector<long long>(N, 0)), dp0(N, vector<long long>(N, 0));
	vector<vector<long long>> rui1(N, vector<long long>(N, 0)), rui0(N, vector<long long>(N, 0));

	for (int i = 0; i < N; i++) {
		for (int j = 0; j < N; j++) {
			if (j > i && S[j - i] == '1') {
				dp1[i][j] = (rui0[i][j - i - 1] + rui1[i][j - 1] + 1) % MOD;
				dp0[i][j] = (rui0[i][j - 1] - rui0[i][j - i - 1] + MOD) % MOD;
			}
			else if (j > i && S[j - i] == '0') {
				dp1[i][j] = rui1[i][j - 1];
				dp0[i][j] = (rui0[i][j - 1] + 1) % MOD;
			}
			else if (j == i && S[0] == '1') {
				dp0[i][j] = (modpow(2, j, MOD) + MOD - 1) % MOD;
				dp1[i][j] = 1;
			}
			else {
				dp0[i][j] = modpow(2, j, MOD);
			}
			if (j > 0) rui1[i][j] = rui1[i][j - 1];
			if (j > 0) rui0[i][j] = rui0[i][j - 1];
			rui1[i][j] = (rui1[i][j] + dp1[i][j]) % MOD;
			rui0[i][j] = (rui0[i][j] + dp0[i][j]) % MOD;
		}
	}

	long long ans = 0;
	long long pow2 = 1;
	for (int i = 0; i < N; i++) {
		ans += pow2 * dp1[i][N - 1] % MOD;
		pow2 = pow2 * 2 % MOD;
	}
	cout << ans % MOD << endl;
}