#include <bits/stdc++.h>
#define fastio ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;

typedef long long LL;
LL MOD = 998244353;

int main() {
    int N;
    cin >> N;
    vector<char> S(N);
    for (int i = 0; i < N; i++) cin >> S[N- 1 - i];
    if (S[0] == '1' || S[1] == '1' || S[N - 1] == '1') {
        cout << 0 << endl;
        return 0;
    }

    // m[A][B][C]: A = (# of 0) - 3*(# of 1) + N / 4, B = min preA, C = 0 or 1
    vector<vector<vector<int>>> m(N+1, vector<vector<int>>(N/2+1, vector<int>(2, 0)));
    m[2+N/4][N/4][0] = 1;
    int miA = 0, maA = 2, maB = 0;
    for (int pos = 2; pos <N;pos++) {
        vector<vector<vector<int>>> mp(N+1, vector<vector<int>>(N/2+1, vector<int>(2, 0)));
        if (S[pos] == '?' || S[pos] == '0') {
            // 0
            for (int a = miA + 1; a <= min(N, maA + 1); a++) {
                for (int b = 0; b <= min(a, N/2); b++) {
                    mp[a][b][0] = (m[a - 1][b][0] + m[a - 1][b][1]) % MOD;
                    miA = min(miA, a);
                    maA = max(maA, a);
                }
            }
        }
        if (S[pos] == '?' || S[pos] == '1') {
            // 1
            for (int a = max(0, miA - 3); a <= min(N-3, maA - 3); a++) {
                for (int b = 0; b <= min(a, N/2); b++) {
                    mp[a][b][1] = m[a+3][b][0];
                    if (a == b && b < N/2) {
                        mp[a][b][1] += m[a+3][b+1][0];
                        mp[a][b][1] %= MOD;
                    }
                    miA = min(miA, a);
                    maA = max(maA, a);
                }
            }
        }
        swap(m, mp);
    }
    LL ans = 0;
    for (int b = 0; b <= N/4; b++) {
        ans += m[N/4][b][0];
        ans %= MOD;
    }
    cout << ans << endl;
}