n, m = map(int, input().split())
mod = 998244353

dp = [[0 for j in range(m + 1)] for i in range(n + 1)]
for i in range(n + 1):
  dp[i][1] = 1
for j in range(1, m + 1):
  dp[0][j] = 1
for i in range(1, n + 1):
  for j in range(2, m + 1):
    dp[i][j] += dp[i][j - 1]
    dp[i][j] += dp[i - 1][m]
    if i - j >= 0:
      dp[i][j] -= dp[i - j][j - 1]
      dp[i][j] += dp[i - j][j]
      dp[i][j] -= dp[i - j][m]
    dp[i][j] %= mod

ans = (pow(m, n, mod) - (dp[n][m] - dp[n - 1][m])) % mod
print(ans)