//#define NDEBUG
#include <cstddef>
#include <cstdint>
#include <vector>

namespace n91 {

using i8 = std::int_least8_t;
using i32 = std::int_least32_t;
using i64 = std::int_least64_t;
using u8 = std::uint_least8_t;
using u32 = std::uint_least32_t;
using u64 = std::uint_least64_t;
using isize = std::ptrdiff_t;
using usize = std::size_t;

class rep {
  const usize f, l;

public:
  class itr {
    friend rep;
    usize i;
    constexpr itr(const usize x) noexcept : i(x) {}

  public:
    void operator++() noexcept { ++i; }
    constexpr usize operator*() const noexcept { return i; }
    constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
  };
  constexpr rep(const usize first, const usize last) noexcept
      : f(first), l(last) {}
  constexpr itr begin() const noexcept { return itr(f); }
  constexpr itr end() const noexcept { return itr(l); }
};
class revrep {
  const usize f, l;

public:
  class itr {
    friend revrep;
    usize i;
    constexpr itr(usize x) noexcept : i(x) {}

  public:
    void operator++() noexcept { --i; }
    constexpr usize operator*() const noexcept { return i; }
    constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
  };
  constexpr revrep(usize first, usize last) noexcept : f(--first), l(--last) {}
  constexpr itr begin() const noexcept { return itr(l); }
  constexpr itr end() const noexcept { return itr(f); }
};
template <class T> using vec_alias = std::vector<T>;
template <class T> auto md_vec(const usize n, const T &value) {
  return std::vector<T>(n, value);
}
template <class... Args> auto md_vec(const usize n, Args... args) {
  return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
}
template <class T> constexpr T difference(const T &a, const T &b) {
  return a < b ? b - a : a - b;
}

} // namespace n91

#include <cstdint>

template <std::uint_fast64_t Modulus> class modint {
  using u64 = std::uint_fast64_t;

public:
  u64 a;

  constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
  constexpr u64 &value() noexcept { return a; }
  constexpr const u64 &value() const noexcept { return a; }
  constexpr modint operator+(const modint rhs) const noexcept {
    return modint(*this) += rhs;
  }
  constexpr modint operator-(const modint rhs) const noexcept {
    return modint(*this) -= rhs;
  }
  constexpr modint operator*(const modint rhs) const noexcept {
    return modint(*this) *= rhs;
  }
  constexpr modint operator/(const modint rhs) const noexcept {
    return modint(*this) /= rhs;
  }
  constexpr modint &operator+=(const modint rhs) noexcept {
    a += rhs.a;
    if (a >= Modulus) {
      a -= Modulus;
    }
    return *this;
  }
  constexpr modint &operator-=(const modint rhs) noexcept {
    if (a < rhs.a) {
      a += Modulus;
    }
    a -= rhs.a;
    return *this;
  }
  constexpr modint &operator*=(const modint rhs) noexcept {
    a = a * rhs.a % Modulus;
    return *this;
  }
  constexpr modint &operator/=(modint rhs) noexcept {
    u64 exp = Modulus - 2;
    while (exp) {
      if (exp % 2) {
        *this *= rhs;
      }
      rhs *= rhs;
      exp /= 2;
    }
    return *this;
  }
};

#include <vector>
namespace n91 {

template <class T> class fact_binom {
public:
  using value_type = T;
  using container_type = std::vector<value_type>;
  using size_type = typename container_type::size_type;

private:
  container_type factrial, inv_fact;

public:
  fact_binom() : factrial(), inv_fact() {}
  explicit fact_binom(const size_type n) : factrial(n + 1), inv_fact(n + 1) {
    factrial[0] = static_cast<value_type>(1);
    for (size_type i = 0; i != n; ++i) {
      factrial[i + 1] = static_cast<value_type>(i + 1) * factrial[i];
    }
    inv_fact[n] = static_cast<value_type>(1) / factrial[n];
    for (size_type i = n; i != 0; --i) {
      inv_fact[i - 1] = inv_fact[i] * static_cast<value_type>(i);
    }
  }

  value_type operator()(const size_type n, const size_type r) const {
    return factrial[n] * inv_fact[r] * inv_fact[n - r];
  }
};

} // namespace n91

#include <algorithm>
#include <iostream>
#include <string>
#include <utility>

namespace n91 {

void main_() {
  using mint = modint<998244353>;
  usize n, x;
  std::cin >> n >> x;
  const usize f_max = (n + x + 1) * 2;
  n91::fact_binom<mint> binom(f_max);
  mint ans = 0;
  if (x % 2 == 0) {
    std::vector<mint> count(n + x + 1);
    for (const auto i : rep(0, x)) {
      for (usize j = 0; j * 2 <= i; ++j) {
        count[i - j] += binom(i - j, j);
      }
    }
    for (usize i = x + 1; i <= 2 * x - 3; i += 2) {
      const usize rem = 2 * x - i - 2;
      for (usize j = 0; j * 2 <= rem; ++j) {
        count[x - 1 - j] += binom(rem - j, j);
      }
    }
    for (const auto i : rep(0, n + 1)) {
      ans += count[i] * binom(n, i);
    }
  } else {
    std::vector<mint> count(n + x + 1);
    if (x != 1) {
      for (const auto i : rep(0, x)) {
        for (usize j = 0; j * 2 <= i; ++j) {
          count[i - j] += binom(i - j, j);
        }
      }
    }
    for (usize i = x + 1; i < 2 * x - 2; i += 2) {
      const usize rem = 2 * x - i - 2;
      for (usize j = 0; j * 2 <= rem; ++j) {
        count[x - 1 - j] += binom(rem - j, j);
      }
    }
    for (usize i = 2 * x - 2; i / 2 <= n; i += 2) {
      count[i / 2] += 1;
    }
    for (const auto i : rep(0, n + 1)) {
      ans += count[i] * binom(n, i);
    }
  }
  std::cout << ans.value() << std::endl;
}

} // namespace n91

int main() {
  n91::main_();
  return 0;
}


Measured memory_bytes: 640