import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }

struct ModInt(uint M_) {
  import std.conv : to;
  alias M = M_;
  uint x;
  this(ModInt a) { x = a.x; }
  this(uint x_) { x = x_ % M; }
  this(ulong x_) { x = cast(uint)(x_ % M); }
  this(int x_) { x = ((x_ %= cast(int)(M)) < 0) ? (x_ + cast(int)(M)) : x_; }
  this(long x_) { x = cast(uint)(((x_ %= cast(long)(M)) < 0) ? (x_ + cast(long)(M)) : x_); }
  ref ModInt opAssign(T)(inout(T) a) if (is(T == uint) || is(T == ulong) || is(T == int) || is(T == long)) { return this = ModInt(a); }
  ref ModInt opOpAssign(string op, T)(T a) {
    static if (is(T == ModInt)) {
      static if (op == "+") { x = ((x += a.x) >= M) ? (x - M) : x; }
      else static if (op == "-") { x = ((x -= a.x) >= M) ? (x + M) : x; }
      else static if (op == "*") { x = cast(uint)((cast(ulong)(x) * a.x) % M); }
      else static if (op == "/") { this *= a.inv(); }
      else static assert(false);
      return this;
    } else static if (op == "^^") {
      if (a < 0) return this = inv()^^(-a);
      ModInt b = this, c = 1U;
      for (long e = a; e; e >>= 1) { if (e & 1) c *= b; b *= b; }
      return this = c;
    } else {
      return mixin("this " ~ op ~ "= ModInt(a)");
    }
  }
  ModInt inv() const {
    uint a = M, b = x; int y = 0, z = 1;
    for (; b; ) { const q = a / b; const c = a - q * b; a = b; b = c; const w = y - cast(int)(q) * z; y = z; z = w; }
    assert(a == 1); return ModInt(y);
  }
  ModInt opUnary(string op)() const {
    static if (op == "+") { return this; }
    else static if (op == "-") { ModInt a; a.x = x ? (M - x) : 0U; return a; }
    else static assert(false);
  }
  ModInt opBinary(string op, T)(T a) const { return mixin("ModInt(this) " ~ op ~ "= a"); }
  ModInt opBinaryRight(string op, T)(T a) const { return mixin("ModInt(a) " ~ op ~ "= this"); }
  bool opCast(T: bool)() const { return (x != 0U); }
  string toString() const { return x.to!string; }
}

enum MO = 998244353;
alias Mint = ModInt!MO;


void main() {
  /*
  debug {{
    bool greedy(in string s) {
      const n = cast(int)(s.length);
      int[] xs, ys;
      for (int i = 0, j; i < n; i = j) {
        for (j = i; j < n && s[i] == s[j]; ++j) {}
        if (s[i] == '0') {
          foreach (k; i .. j) {
            xs ~= k;
          }
        } else {
          ys ~= i;
        }
      }
      if (xs.length % 2 != 0) {
        return false;
      }
      const len = xs.length / 2;
      int l;
      foreach (k; 0 .. len) {
        for (; ; ) {
          if (l == ys.length) {
            return false;
          }
          if (xs[k] < ys[l]) {
            if (ys[l] < xs[len + k]) {
              ++l;
              break;
            } else {
              return false;
            }
          } else {
            ++l;
          }
        }
      }
      return true;
    }
    
    enum lim = 16;
    auto dp = new bool[][lim];
    dp[0] = [true];
    foreach (n; 1 .. lim) {
      dp[n] = new bool[1 << n];
      foreach (p; 0 .. 1 << n) {
        foreach (i; 0 .. n) if (p >> i & 1) {
          if (dp[n - 1][(p & ((1 << i) - 1)) | (p >> (i + 1) << i)]) {
            dp[n][p] = true;
          }
        }
        foreach (i; 0 .. n - 2) if ((p >> i & 7) == 2) {
          if (dp[n - 3][(p & ((1 << i) - 1)) | (p >> (i + 3) << i)]) {
            dp[n][p] = true;
          }
        }
      }
      int cnt;
      foreach (p; 0 .. 1 << n) {
        const s = iota(n).map!(i => "01"[p >> i & 1]).array;
        if (dp[n][p]) {
          ++cnt;
          writeln(s);
        }
        const grd = greedy(s);
        assert(dp[n][p] == grd, format("%s: %s %s", s, dp[n][p], grd));
      }
      stderr.writeln(n, ": ", cnt);
      stderr.flush;
    }
    return;
  }}
  //*/
/*
1: 1
2: 1
3: 2
4: 4
5: 7
6: 14
7: 29
8: 57
9: 114
10: 232
11: 465
12: 931
13: 1876
14: 3767
15: 7548
*/
  
  try {
    for (; ; ) {
      const N = readInt;
      auto S = readToken;
      
      auto crt = new Mint[2][][](N / 2 + 1, N / 2 + 1);
      auto CRT = new Mint[2][][](N / 2 + 1, N / 2 + 1);
      crt[0][0][0] = 1;
      foreach (i; 0 .. N) {
        auto nxt = new Mint[2][][](N / 2 + 1, N / 2 + 1);
        auto NXT = new Mint[2][][](N / 2 + 1, N / 2 + 1);
        const can0 = (S[i] == '?' || S[i] == '0');
        const can1 = (S[i] == '?' || S[i] == '1');
        foreach (a; 0 .. min(i, N / 2) + 1) foreach (b; 0 .. min(i - a, N / 2) + 1) {
          static foreach (s; 0 .. 2) if (crt[a][b][s]) {
            // 0
            if (can0 && a + 1 <= N / 2) {
              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];
            }
          }
        }
        foreach (a; 0 .. min(i, N / 2) + 1) foreach (b; 0 .. min(i - a, N / 2) + 1) {
          static foreach (s; 0 .. 2) 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];
            }
          }
        }
        crt = nxt;
        CRT = NXT;
      }
      
      Mint ans;
      static foreach (s; 0 .. 2) {
        ans += crt[0][0][s];
        ans += CRT[0][0][s];
      }
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}