import sys
input = sys.stdin.readline
from collections import *


# def f(i, j):
#     return pow(j-i+1, N-1, MOD)*(i+j)*(j-i+1)//2*N

# N, M = map(int, input().split())
# ans = 0
# MOD = 998244353

# for i in range(1, M+1):
#     for j in range(i+1, M+1):
#         #ans += (j-i)*(f(i, j)-f(i, j-1)-f(i+1, j)+f(i+1, j-1))
#         ans += (j-i)*(f(i, j)-f(i, j-1)-f(i+1, j)+f(i+1, j-1))
#         ans %= MOD

# print(ans)


N, M = map(int, input().split())
imos1 = [0]*(M+1)
imos2 = [0]*(M+1)

for i in range(1, M+1):
    l = i-1
    r = M-i
    imos1[1] += i
    imos1[l+1] -= i
    imos1[1] += i
    imos1[r+1] -= i
    imos2[1] += 1
    imos2[l+1] -= 1
    imos2[1] += 1
    imos2[r+1] -= 1

for i in range(1, M+1):
    imos1[i] += imos1[i-1]
    imos2[i] += imos2[i-1]
    
ans = 0
MOD = 998244353
power = []

for i in range(M+1):
    power.append(pow(i, N-1, MOD))
    
inv2 = pow(2, MOD-2, MOD)

for d in range(1, M):
    ans += d*power[d+1]%MOD*(d+1)%MOD*inv2%MOD*N%MOD*imos1[d]%MOD
    ans %= MOD
    ans -= d*power[d]%MOD*d%MOD*inv2%MOD*N%MOD*(imos1[d]-imos2[d])%MOD
    ans %= MOD
    ans -= d*power[d]%MOD*d%MOD*inv2%MOD*N%MOD*(imos1[d]+imos2[d])%MOD
    ans %= MOD
    ans += d*power[d-1]%MOD*(d-1)%MOD*inv2%MOD*N%MOD*imos1[d]%MOD
    ans %= MOD

print(ans)