#include <bits/stdc++.h>
using namespace std;
long long A[1010][2010], B[1010][2010];
int main() {
  int n, k;
  cin >> n >> k;
  A[1][1] = 2;
  B[1][2] = 2;
  for (int i = 2; i <= n; i++) {
    for (int j = 1; j <= 2 * i; j++) {
      A[i][j] = (A[i - 1][j - 1] + A[i - 1][j] + 2 * B[i - 1][j]) % 998244353;
      B[i][j] =
          (2 * A[i - 1][j - 1] + B[i - 1][j] + B[i - 1][j - 2]) % 998244353;
    }
  }
  cout << (A[n][k] + B[n][k]) % 998244353 << endl;
  return 0;
}

### Prompt

Develop a solution in CPP to the problem described below:

You are given a grid, consisting of 2 rows and n columns. Each cell of this grid should be colored either black or white.

Two cells are considered neighbours if they have a common border and share the same color. Two cells A and B belong to the same component if they are neighbours, or if there is a neighbour of A that belongs to the same component with B.

Let's call some bicoloring beautiful if it has exactly k components.

Count the number of beautiful bicolorings. The number can be big enough, so print the answer modulo 998244353.

Input

The only line contains two integers n and k (1 ≤ n ≤ 1000, 1 ≤ k ≤ 2n) — the number of columns in a grid and the number of components required.

Output

Print a single integer — the number of beautiful bicolorings modulo 998244353.

Examples

Input

3 4


Output

12


Input

4 1


Output

2


Input

1 2


Output

2

Note

One of possible bicolorings in sample 1:

<image>

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
long long A[1010][2010], B[1010][2010];
int main() {
  int n, k;
  cin >> n >> k;
  A[1][1] = 2;
  B[1][2] = 2;
  for (int i = 2; i <= n; i++) {
    for (int j = 1; j <= 2 * i; j++) {
      A[i][j] = (A[i - 1][j - 1] + A[i - 1][j] + 2 * B[i - 1][j]) % 998244353;
      B[i][j] =
          (2 * A[i - 1][j - 1] + B[i - 1][j] + B[i - 1][j - 2]) % 998244353;
    }
  }
  cout << (A[n][k] + B[n][k]) % 998244353 << endl;
  return 0;
}

```