#include <bits/stdc++.h> //#include <atcoder/all> //using namespace atcoder; #pragma GCC target ("avx2") #pragma GCC optimization ("O3") #pragma GCC optimization ("unroll-loops") using namespace std; typedef vector<int> VI; typedef vector<VI> VVI; typedef vector<string> VS; typedef pair<int, int> PII; typedef pair<int, int> pii; typedef pair<long long, long long> PLL; typedef pair<int, PII> TIII; typedef long long ll; typedef long double ld; typedef unsigned long long ull; #define FOR(i, s, n) for (int i = s; i < (int)n; ++i) #define REP(i, n) FOR(i, 0, n) #define rep(i, a, b) for (int i = a; i < (b); ++i) #define trav(a, x) for (auto &a : x) #define all(x) x.begin(), x.end() #define MOD 1000000007 template<class T1, class T2> inline bool chmax(T1 &a, T2 b) {if (a < b) {a = b; return true;} return false;} template<class T1, class T2> inline bool chmin(T1 &a, T2 b) {if (a > b) {a = b; return true;} return false;} const double EPS = 1e-10, PI = acos(-1); const double pi = 3.141592653589793238462643383279; //ここから編集 typedef string::const_iterator State; ll GCD(ll a, ll b){ return (b==0)?a:GCD(b, a%b); } ll LCM(ll a, ll b){ return a/GCD(a, b) * b; } template<typename T> string tobin(T n) { string res = ""; while(n) { res += (char)('0' + n%2); n>>=2; } reverse(all(res)); return res; } template<typename T> vector<vector<T>> rotateMatrixclockwise(vector<vector<T>> v) { int n = v.size(), m = v[0].size(); vector<vector<T>> res(m, vector<T>(n)); REP(i,n) REP(j,m) res[j][n-i-1] = v[i][j]; return res; } template< int mod > struct ModInt { int x; ModInt() : x(0) {} ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {} ModInt &operator+=(const ModInt &p) { if((x += p.x) >= mod) x -= mod; return *this; } ModInt &operator-=(const ModInt &p) { if((x += mod - p.x) >= mod) x -= mod; return *this; } ModInt &operator*=(const ModInt &p) { x = (int) (1LL * x * p.x % mod); return *this; } ModInt &operator/=(const ModInt &p) { *this *= p.inverse(); return *this; } ModInt operator-() const { return ModInt(-x); } ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; } ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; } ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; } ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; } bool operator==(const ModInt &p) const { return x == p.x; } bool operator!=(const ModInt &p) const { return x != p.x; } ModInt inverse() const { int a = x, b = mod, u = 1, v = 0, t; while(b > 0) { t = a / b; swap(a -= t * b, b); swap(u -= t * v, v); } return ModInt(u); } ModInt pow(int64_t n) const { ModInt ret(1), mul(x); while(n > 0) { if(n & 1) ret *= mul; mul *= mul; n >>= 1; } return ret; } friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; } friend istream &operator>>(istream &is, ModInt &a) { int64_t t; is >> t; a = ModInt< mod >(t); return (is); } static int get_mod() { return mod; } }; using modint = ModInt< 998244353 >; template< typename T > struct Combination { vector< T > _fact, _rfact, _inv; Combination(int sz) : _fact(sz + 1), _rfact(sz + 1), _inv(sz + 1) { _fact[0] = _rfact[sz] = _inv[0] = 1; for(int i = 1; i <= sz; i++) _fact[i] = _fact[i - 1] * i; _rfact[sz] /= _fact[sz]; for(int i = sz - 1; i >= 0; i--) _rfact[i] = _rfact[i + 1] * (i + 1); for(int i = 1; i <= sz; i++) _inv[i] = _rfact[i] * _fact[i - 1]; } inline T fact(int k) const { return _fact[k]; } inline T rfact(int k) const { return _rfact[k]; } inline T inv(int k) const { return _inv[k]; } T P(int n, int r) const { if(r < 0 || n < r) return 0; return fact(n) * rfact(n - r); } T C(int p, int q) const { if(q < 0 || p < q) return 0; return fact(p) * rfact(q) * rfact(p - q); } T H(int n, int r) const { if(n < 0 || r < 0) return (0); return r == 0 ? 1 : C(n + r - 1, r); } }; ll modpow(ll x, ll n, ll mod) { ll res = 1; x %= mod; if(x == 0) return 0; while(n) { if(n&1) res = (res * x) % mod; x = (x * x) % mod; n >>= 1; } return res; } inline long long mod(long long a, long long m) { return (a % m + m) % m; } template<typename T> struct BIT{ int N; std::vector<T> node; BIT(){} BIT(int n){ N = n; node.resize(N+10); } void build(int n) { N = n; node.resize(N+10); } /* a: 1-idxed */ void add(int a, T x){ for(int i=a; i<(int)node.size(); i += i & -i) node[i] += x; } /* [1, a] */ T sum(int a){ T res = 0; for(int x=a; x>0; x -= x & -x) res += node[x]; return res; } /* [l, r] */ T rangesum(int l, int r){ if(l > r) return 0; return sum(r) - sum(l-1); } /* a1+a2+...+aw >= valとなるような最小のwを返す @verify https://codeforces.com/contest/992/problem/E */ int lower_bound(T val) { if(val < 0) return 0; int res = 0; int n = 1; while (n < N) n *= 2; T tv=0; for (int k = n; k > 0; k /= 2) { if(res + k < N && node[res + k] < val){ val -= node[res+k]; res += k; } } return res+1; } }; struct UnionFind{ std::vector<int> par; std::vector<int> siz; UnionFind(int sz_): par(sz_), siz(sz_) { for(int i=0; i<sz_; ++i) par[i] = i, siz[i] = 1; } void init(int sz_){ par.resize(sz_); siz.resize(sz_); for(int i=0; i<sz_; ++i) par[i] = i, siz[i] = 1; } int root(int x){ if(x == par[x]) return x; return par[x] = root(par[x]); } bool merge(int x, int y){ x = root(x), y = root(y); if(x == y) return false; if(siz[x] < siz[y]) std::swap(x, y); siz[x] += siz[y]; par[y] = x; return true; } bool issame(int x, int y){ return root(x) == root(y); } int size(int x){ return siz[root(x)]; } }; struct RollingHash{ using ull = unsigned long long; const ull mod = (1ULL << 61) - 1; const ull MASK30 = (1ULL << 30) - 1; const ull MASK31 = (1ULL << 31) - 1; const ull MASK61 = mod; ull base; int n; vector<ull> hash, pow; RollingHash(const string &s) { random_device rnd; mt19937_64 mt(rnd()); base = 1001; n = (int)s.size(); hash.assign(n+1, 0); pow.assign(n+1, 1); for(int i=0; i<n; i++){ hash[i+1] = calc_mod(mul(hash[i], base) + s[i]); pow[i+1] = calc_mod(mul(pow[i], base)); } } ull calc_mod(ull x){ ull xu = x >> 61; ull xd = x & MASK61; ull res = xu + xd; if(res >= mod) res -= mod; return res; } ull mul(ull a, ull b){ ull au = a >> 31; ull ad = a & MASK31; ull bu = b >> 31; ull bd = b & MASK31; ull mid = ad * bu + au * bd; ull midu = mid >> 30; ull midd = mid & MASK30; return calc_mod(au * bu * 2 + midu + (midd << 31) + ad * bd); } //[l,r)のハッシュ値 inline ull get(int l, int r){ ull res = calc_mod(hash[r] + mod*3-mul(hash[l], pow[r-l])); return res; } //string tのハッシュ値 inline ull get(string t){ ull res = 0; for(int i=0; i<t.size(); i++){ res = calc_mod(mul(res, base)+t[i]); } return res; } //string s中のtの数をカウント inline int count(string t) { if(t.size() > n) return 0; auto hs = get(t); int res = 0; for(int i=0; i<n-t.size()+1; i++){ if(get(i, i+t.size()) == hs) res++; } return res; } /* concat @verify https://codeforces.com/problemset/problem/514/C */ inline ull concat(ull h1, ull h2, int h2len){ return calc_mod(h2 + mul(h1, pow[h2len])); } // LCPを求める S[a:] T[b:] inline int LCP(int a, int b){ int len = min((int)hash.size()-a, (int)hash.size()-b); int lb = -1, ub = len; while(ub-lb>1){ int mid = (lb+ub)/2; if(get(a, a+mid) == get(b, b+mid)) lb = mid; else ub = mid; } return lb; } }; template <typename Monoid> struct SegmentTree{ int N; vector<Monoid> node; Monoid Unit; function<Monoid(Monoid, Monoid)> f; SegmentTree(vector<Monoid> v, const function<Monoid(Monoid, Monoid)> f, const Monoid &Unit): f(f), Unit(Unit){ int sz_ = v.size(); N = 1; while(N < sz_) N *= 2; node.assign(2*N, Unit); for(int i=0; i<sz_; i++) node[i+N-1] = v[i]; for(int i=N-2; i>=0; i--) node[i] = f(node[2*i+1], node[2*i+2]); } void update(int k, const Monoid &x) { k += N-1; node[k] = x; while(k > 0){ k = (k-1)/2; node[k] = f(node[2*k+1], node[2*k+2]); } } Monoid query(int a, int b, int k=0, int l = 0, int r=-1){ if(r < 0) r = N; if(r <= a || b <= l) return Unit; if(a <= l && r <= b) return node[k]; else{ Monoid vl = query(a, b, 2*k+1, l, (l+r)/2); Monoid vr = query(a, b, 2*k+2, (l+r)/2, r); return f(vl, vr); } } inline Monoid operator[](int a) { return query(a, a + 1); } }; int main() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); int N, K; cin >> N >> K; modint ans = 0; modint A = modint(K).pow(N); auto get = [&](ll x) { if(x > K) return modint(0); return A - modint(x-1).pow(N) - (modint(x-1).pow(N-1) * (K-x+1) * N); }; for(int i=1; i<=K; i++) { ans += (get(i) - get(i+1)) * i; } cout << ans << endl; return 0; }