#include<bits/stdc++.h>
using namespace std;

#define rep(i, a, n) for(int i=(a); i<(n); ++i)
#define per(i, a, n) for(int i=(a); i>(n); --i)
#define pb emplace_back
#define mp make_pair
#define clr(a, b) memset(a, b, sizeof(a))
#define all(x) (x).begin(),(x).end()
#define lowbit(x) (x & -x)
#define fi first
#define se second
#define lson o<<1
#define rson o<<1|1
#define gmid l[o]+r[o]>>1

using LL = long long;
using ULL = unsigned long long;
using pii = pair<int,int>;
using PLL = pair<LL, LL>;
using UI = unsigned int;

const int mod = 998244353;
const int inf = 0x3f3f3f3f;
const double EPS = 1e-8;
const double PI = acos(-1.0);

const int N = 5e5 + 10;
LL a[N], sum[N];
LL n;
int m;

LL pow_mod(LL x, LL p){
	LL s = 1;
	while(p){
		if(p & 1)	s = s * x % mod;
		x = x * x % mod;
		p >>= 1;
	}
	return s;
}

int main(){
	scanf("%lld %d", &n, &m);
	sum[0] = a[0] = 0;
	rep(i, 1, m + 1){
		sum[i] = (sum[i-1] + i) % mod;
		a[i] = pow_mod(i, n - 1);
	}

	LL ans = 0;

	rep(i, 1, m + 1){
		ans = ans + (sum[i] * a[i] % mod + mod - sum[i-1] * a[i-1] % mod) % mod * i % mod;
		ans = ans + ((sum[m] + mod - sum[i-1]) * a[m-i+1] % mod + mod - (sum[m] + mod - sum[i]) % mod * a[m-i]) % mod * (mod - i) % mod;
		ans = ans % mod;
	}
	printf("%lld\n", n % mod * ans % mod);

	
	return 0;
}