# https://yukicoder.me/problems/no/2883

MOD = 998244353

def prod_matrix(left, right):
    n = len(left)
    new_matrix = [[0] * n for _ in range(n)]
    for i in range(n):
        for j in range(n):
            for k in range(n):
                new_matrix[i][j] += (left[i][k] * right[k][j]) % MOD
                new_matrix[i][j] %= MOD
    return new_matrix

def prod_vector(matrix, vector):
    n = len(vector)
    new_vector = [0] * n
    for i in range(n):
        for j in range(n):
            new_vector[i] += (matrix[i][j] * vector[j] ) % MOD
            new_vector[i] %= MOD
    return new_vector


class CombinationCalculator:
    """
    modを考慮したPermutation, Combinationを計算するためのクラス
    """    
    def __init__(self, size, mod):
        self.mod = mod
        self.factorial = [0] * (size + 1)
        self.factorial[0] = 1
        for i in range(1, size + 1):
            self.factorial[i] = (i * self.factorial[i - 1]) % self.mod
        
        self.inv_factorial = [0] * (size + 1)
        self.inv_factorial[size] = pow(self.factorial[size], self.mod - 2, self.mod)

        for i in reversed(range(size)):
            self.inv_factorial[i] = ((i + 1) * self.inv_factorial[i + 1]) % self.mod

    def calc_combination(self, n, r):
        if n < 0 or n < r or r < 0:
            return 0

        if r == 0 or n == r:
            return 1
        
        ans = self.inv_factorial[n - r] * self.inv_factorial[r]
        ans %= self.mod
        ans *= self.factorial[n]
        ans %= self.mod
        return ans
    
    def calc_permutation(self, n, r):
        if n < 0 or n < r:
            return 0

        ans = self.inv_factorial[n - r]
        ans *= self.factorial[n]
        ans %= self.mod
        return ans
        

def main():
    N, K = map(int, input().split())
    combi = CombinationCalculator(K + 1, MOD)

    if N == 1:
        print(1)
        return
    elif N == 2:
        print(2)
        return


    matrix = [[0] * (K + 1) for _ in range(K + 1)]
    for i in range(K + 1):
        for j in reversed(range(K - i, K + 1)):
            matrix[i][j] = combi.calc_combination(i, K - j)
    side_matrix = [[0] * (K + 1) for _ in range(K + 1)]
    for i in range(K + 1):
        side_matrix[i][i] = 1
    matrix2 = [[0] * (K + 1) for _ in range(K + 1)]
    for i in range(K + 1):
        matrix2[i][i] = 1
    side_matrix2 = [[0] * (K + 1) for _ in range(K + 1)]
    
    vector = [1] * (K + 1)
    N -= 2
    while N > 0:
        if N % 2 == 1:
            matrix2 = prod_matrix(matrix, matrix2)
            side_matrix2 = prod_matrix(matrix, side_matrix2) 
            for i in range(K + 1):
                for j in range(K + 1):
                    side_matrix2[i][j] += side_matrix[i][j]
                    side_matrix2[i][j] %= MOD


        base = prod_matrix(matrix, matrix)
        base2 = prod_matrix(matrix, side_matrix) 
        for i in range(K + 1):
            for j in range(K + 1):
                side_matrix[i][j] += base2[i][j]
                side_matrix[i][j] %= MOD
        matrix = base
        N //= 2

    v1 = prod_vector(matrix2, vector)
    v2 = prod_vector(side_matrix2, vector)
    ans = (v1[K] + v2[K]) % MOD
    print((ans + 1) % MOD)
        









if __name__ == "__main__":
    main()