import sys
from collections import defaultdict, Counter, deque
from itertools import permutations, combinations, product, combinations_with_replacement, groupby, accumulate
import operator
from math import sqrt, gcd, factorial
# from math import isqrt, prod,comb  # python3.8用(notpypy)
#from bisect import bisect_left,bisect_right
#from functools import lru_cache,reduce
#from heapq import heappush,heappop,heapify,heappushpop,heapreplace
#import numpy as np
#import networkx as nx
#from networkx.utils import UnionFind
#from numba import njit, b1, i1, i4, i8, f8
#from scipy.sparse import csr_matrix
#from scipy.sparse.csgraph import shortest_path, floyd_warshall, dijkstra, bellman_ford, johnson, NegativeCycleError
# numba例 @njit(i1(i4[:], i8[:, :]),cache=True) 引数i4配列、i8 2次元配列,戻り値i1
def input(): return sys.stdin.readline().rstrip()
def divceil(n, k): return 1+(n-1)//k  # n/kの切り上げを返す
def yn(hantei, yes='Yes', no='No'): print(yes if hantei else no)


class PrepereFactorial2:  # maxnumまでの階乗を事前計算して、順列、組み合わせ、重複組み合わせを計算するクラス。逆元のテーブルもpow無しで前計算する。maxnumに比べて関数呼び出しが多いならこちら
    def __init__(self, maxnum=3*10**5, mod=10**9+7):
        self.factorial = [1]*(maxnum+1)
        modinv_table = [-1] * (maxnum+1)
        modinv_table[1] = 1
        for i in range(2, maxnum+1):
            self.factorial[i] = (self.factorial[i-1]*i) % mod
            modinv_table[i] = (-modinv_table[mod % i] * (mod // i)) % mod
        self.invfactorial = [1]*(maxnum+1)
        for i in range(1, maxnum+1):
            self.invfactorial[i] = self.invfactorial[i-1]*modinv_table[i] % mod
        self.mod = mod

    def permutation(self, n, r):
        return self.factorial[n]*self.invfactorial[n-r] % self.mod

    def combination(self, n, r):
        if r > n:
            return 0
        return self.permutation(n, r)*self.invfactorial[r] % self.mod

    def combination_with_repetition(self, n, r):
        return self.combination(n+r-1, r)


def main():
    mod = 10**9+7
    mod2 = 998244353
    n, m = map(int, input().split())
    """
    if n==1:
        print(0)
        return
    """
    ans = 0
    inv2 = pow(2, mod2-2, mod2)
    for i in range(1, m):  # i:幅
        med = 2+i
        lens = m-i
        ans += (pow(i+1, n, mod2)-pow(i,n,mod2)*2+pow(i-1,n,mod2))*n*(med+lens-1)*lens*inv2*i
    print(ans % mod2)


if __name__ == '__main__':
    main()