import sys,random,bisect
from collections import deque,defaultdict
from heapq import heapify,heappop,heappush
from itertools import permutations
from math import gcd

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

mod = 998244353

N,M = mi()

dp = [0] * (N+1)
dp_last = [[0 for j in range(M+1)] for i in range(N+1)]

dp_cum = [0] * (N+1)
dp_last_cum = [[0 for j in range(M+1)] for i in range(N+1)]

for j in range(2,M+1):
    dp_last[1][j] = 1
    dp_last_cum[1][j] = 1
dp[1] = M-1
dp_cum[1] = M-1

for i in range(2,N+1):
    for j in range(2,M+1):
        #dp_last[i][j] = sum(dp[i-l]-dp_last[i-l][j] for l in range(1,j)) % mod
        if j <= i:
            dp_last[i][j] = (dp_cum[i-1]-dp_cum[i-j]) - (dp_last_cum[i-1][j]-dp_last_cum[i-j][j]) % mod
        else:
            dp_last[i][j] = dp_cum[i-1] -dp_last_cum[i-1][j] + 1 
        dp_last[i][j] %= mod
        dp_last_cum[i][j] = (dp_last_cum[i-1][j] + dp_last[i][j]) % mod
        dp[i] += dp_last[i][j]
        dp[i] %= mod
    dp_cum[i] = (dp[i] + dp_cum[i-1]) % mod

res = pow(M,N,mod) - dp[N]

print(res % mod)