MOD = 998244353

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

def geometric_progression(a, r, n):
    # a = 初項 r = 公比 n = 項数
    if r == 1:
        return a*n%MOD
    return a*((pow(r, n, MOD)-1)%MOD)%MOD*inverse(1, r-1)%MOD

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

ans = 0
for m in range(1, M+1):
    ans += m*geometric_progression((M-m+1)*pow(M, N-1, MOD)%MOD, (M-m+1)*inverse(1, M)%MOD, N)%MOD
    ans %= MOD
    if m < M:
        ans -= m*geometric_progression((M-m)*pow(M, N-1, MOD)%MOD, (M-m)*inverse(1, M)%MOD, N)%MOD
        ans %= MOD

print(ans)