def main():
    mod = 998244353
    N,M = map(int,input().split())
    mx = 0
    pown = [0]
    for i in range(1,M+1):
        temp = pow(i,N-1,mod)
        pown.append(temp)


    for i in range(1,M+1): #1-M
        #temp = (i*(i+1)//2)*pow(i,N-1,mod)*N - ((i-1)*i//2)*pow(i-1,N-1,mod)*N
        temp = (i*(i+1)//2)*pown[i]*N - ((i-1)*i//2)*pown[i-1]*N
        mx += temp*i
        mx %= mod
    mn = 0
    for i in range(1,M+1):
        temp = ((M+i)*(M-i+1)//2)*pown[M-i+1]*N - ((M+i+1)*(M-i)//2)*pown[M-i]*N
        mn += temp*i
        mn %= mod
    
    ans = mx - mn
    print(ans%mod)


if __name__ == '__main__':
    main()