#pragma GCC optimize ("Ofast")
#pragma GCC optimize ("unroll-loops")

#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }

////////////////////////////////////////////////////////////////////////////////
template <unsigned M_> struct ModInt {
  static constexpr unsigned M = M_;
  unsigned x;
  constexpr ModInt() : x(0U) {}
  constexpr ModInt(unsigned x_) : x(x_ % M) {}
  constexpr ModInt(unsigned long long x_) : x(x_ % M) {}
  constexpr ModInt(int x_) : x(((x_ %= static_cast<int>(M)) < 0) ? (x_ + static_cast<int>(M)) : x_) {}
  constexpr ModInt(long long x_) : x(((x_ %= static_cast<long long>(M)) < 0) ? (x_ + static_cast<long long>(M)) : x_) {}
  ModInt &operator+=(const ModInt &a) { x = ((x += a.x) >= M) ? (x - M) : x; return *this; }
  ModInt &operator-=(const ModInt &a) { x = ((x -= a.x) >= M) ? (x + M) : x; return *this; }
  ModInt &operator*=(const ModInt &a) { x = (static_cast<unsigned long long>(x) * a.x) % M; return *this; }
  ModInt &operator/=(const ModInt &a) { return (*this *= a.inv()); }
  ModInt pow(long long e) const {
    if (e < 0) return inv().pow(-e);
    ModInt a = *this, b = 1U; for (; e; e >>= 1) { if (e & 1) b *= a; a *= a; } return b;
  }
  ModInt inv() const {
    unsigned a = M, b = x; int y = 0, z = 1;
    for (; b; ) { const unsigned q = a / b; const unsigned c = a - q * b; a = b; b = c; const int w = y - static_cast<int>(q) * z; y = z; z = w; }
    assert(a == 1U); return ModInt(y);
  }
  ModInt operator+() const { return *this; }
  ModInt operator-() const { ModInt a; a.x = x ? (M - x) : 0U; return a; }
  ModInt operator+(const ModInt &a) const { return (ModInt(*this) += a); }
  ModInt operator-(const ModInt &a) const { return (ModInt(*this) -= a); }
  ModInt operator*(const ModInt &a) const { return (ModInt(*this) *= a); }
  ModInt operator/(const ModInt &a) const { return (ModInt(*this) /= a); }
  template <class T> friend ModInt operator+(T a, const ModInt &b) { return (ModInt(a) += b); }
  template <class T> friend ModInt operator-(T a, const ModInt &b) { return (ModInt(a) -= b); }
  template <class T> friend ModInt operator*(T a, const ModInt &b) { return (ModInt(a) *= b); }
  template <class T> friend ModInt operator/(T a, const ModInt &b) { return (ModInt(a) /= b); }
  explicit operator bool() const { return x; }
  bool operator==(const ModInt &a) const { return (x == a.x); }
  bool operator!=(const ModInt &a) const { return (x != a.x); }
  friend std::ostream &operator<<(std::ostream &os, const ModInt &a) { return os << a.x; }
};
////////////////////////////////////////////////////////////////////////////////

constexpr unsigned MO = 998244353;
using Mint = ModInt<MO>;


int N;
char S[1510];

Mint dp[2][510][510][2];
Mint DP[2][510][510][2];

int main() {
  for (; ~scanf("%d", &N); ) {
    scanf("%s", S);
    
    const int L = N / 3;
    
    memset(dp, 0, sizeof(dp));
    memset(DP, 0, sizeof(DP));
    dp[0][0][0][0] = 1;
    for (int i = 0; i < N; ++i) {
      auto crt = dp[i & 1], nxt = dp[(i + 1) & 1];
      auto CRT = DP[i & 1], NXT = DP[(i + 1) & 1];
      memset(nxt, 0, sizeof(dp[0]));
      memset(NXT, 0, sizeof(DP[0]));
      const bool can0 = (S[i] == '?' || S[i] == '0');
      const bool can1 = (S[i] == '?' || S[i] == '1');
      const int lim = min({i, N - i, L});
      for (int a = 0; a <= lim; ++a) for (int b = 0; b <= lim - a; ++b) {
        for (int s = 0; s < 2; ++s) if (crt[a][b][s]) {
          // 0
          if (can0 && a + 1 + b <= L) {
            nxt[a + 1][b][0] += crt[a][b][s];
          }
          // 1
          if (can1) {
            if (!s && a) {
              nxt[a - 1][b + 1][1] += crt[a][b][s];
            } else {
              nxt[a][b][1] += crt[a][b][s];
            }
          }
          // 2
          if (can0 && b) {
            NXT[a][b - 1][0] += crt[a][b][s];
          }
        }
      }
      for (int a = 0; a <= lim; ++a) for (int b = 0; b <= lim - a; ++b) {
        for (int s = 0; s < 2; ++s) if (CRT[a][b][s]) {
          // 1
          if (can1) {
            if (!s && a) {
              NXT[a - 1][b + 1][1] += CRT[a][b][s];
            } else {
              NXT[a][b][1] += CRT[a][b][s];
            }
          }
          // 2
          if (can0 && b) {
            NXT[a][b - 1][0] += CRT[a][b][s];
          }
        }
      }
    }
    
    Mint ans = 0;
    for (int s = 0; s < 2; ++s) {
      ans += dp[N & 1][0][0][s];
      ans += DP[N & 1][0][0][s];
    }
    printf("%u\n", ans.x);
  }
  return 0;
}