MOD = 998244353

def matrix(a, b):
    ans = [[0]*len(b[0]) for _ in range(len(a))]
    for i in range(len(a)):
        for j in range(len(b[0])):
            for k in range(len(b)):
                ans[i][j] += a[i][k]*b[k][j]%MOD
                ans[i][j] %= MOD
    return ans

def inverse(n, d):
    return n * pow(d, -1, MOD) % MOD

def geometric_progression(a, r, n):
    ans = [[0] for _ in range(2)]
    ans[0][0] = a
    mat = [[r, 0], [1, 1]]
    for i in range(60):
        if 1<<i & n:
            ans = matrix(mat, ans)
        mat = matrix(mat, mat)
    return ans[1][0]

N, M = map(int, input().split())

if N == 1:
    exit(print(0))
if M == 1:
    exit(print(N%2^1))

N -= 1
ans = 0
if N%2 == 1:
    l, r = 1, N
    ans += geometric_progression(M%MOD, M*M%MOD, (r-l)//2+1)
    ans %= MOD
    l, r = 2, N-1
    ans -= geometric_progression(M*M%MOD, M*M%MOD, (r-l)//2+1)
    ans %= MOD
else:
    l, r = 2, N
    ans += geometric_progression(M*M%MOD, M*M%MOD, (r-l)//2+1)
    ans %= MOD
    l, r = 1, N-1
    ans -= geometric_progression(M%MOD, M*M%MOD, (r-l)//2+1)
    ans %= MOD

print(ans)