using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static long NN => long.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        WriteLine(Dice(n, m));
    }
    static long Dice(long n, long m)
    {
        var ans = 0L;
        var mod = 998_244_353;
        var rev2 = 499_122_177;
        var nc = n % mod;
        var exp = new long[m + 1];
        exp[1] = 1;
        for (var i = 2; i < exp.Length; ++i) exp[i] = Exp(i, n - 1, mod);
        for (var i = 1; i < m; ++i)
        {
            if (i == 1)
            {
                var tb = (exp[i + 1] - exp[i] + mod) % mod * nc % mod;
                var count = tb * 2 % mod;
                var add = (tb * (i + 2) % mod * (m - i) % mod + count % mod * (m - 2) % mod * (m - 1) % mod * rev2 % mod) * i % mod;
                ans = (ans + add) % mod;
            }
            else
            {
                var tb = (exp[i + 1] - exp[i] + mod) % mod * nc % mod;
                var mid = (exp[i + 1] - exp[i] * 2 + exp[i - 1] + mod + mod) % mod * nc % mod;
                var count = (tb * 2 + mid * (i - 1) % mod) % mod;
                var add = ((tb * (i + 2) % mod + (i * (i + 1L) % mod * rev2 % mod - 1 + mod) % mod * mid % mod) % mod * (m - i) % mod
                    + count % mod * (m - i - 1) % mod * (m - i) % mod * rev2 % mod) * i % mod;
                ans = (ans + add) % mod;
            }
        }
        return ans;
    }
    static long Exp(long n, long p, int mod)
    {
        long _n = n % mod;
        var _p = p;
        var result = 1L;
        if ((_p & 1) == 1) result *= _n;
        while (_p > 0)
        {
            _n = _n * _n % mod;
            _p >>= 1;
            if ((_p & 1) == 1) result = result * _n % mod;
        }
        return result;
    }
}