#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
long long add(long long x, long long y, long long CMOD = MOD) {
  return (x + y + CMOD + CMOD) % CMOD;
}
long long mult(long long x, long long y, long long CMOD = MOD) {
  return add(x, 0) * add(y, 0) % CMOD;
}
long long fast_expo(long long x, long long y, long long CMOD = MOD) {
  if (x == 0) return 0;
  if (y == 0) return 1;
  long long ans = fast_expo(x, y / 2, CMOD);
  ans = mult(ans, ans, CMOD);
  if (y & 1) ans = mult(ans, x, CMOD);
  return ans;
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
long long gen(long long x, long long y) {
  if (x == y) return x;
  return x + rng() % (y - x + 1);
}
const int TAM = 2e5 + 100;
const long long INF = LLONG_MAX / 4;
long long fact[TAM];
long long ifact[TAM];
long long n, m;
void pre() {
  fact[0] = 1;
  for (int i = 1; i < TAM; i++) fact[i] = mult(fact[i - 1], i);
  for (int i = 0; i < TAM; i++) ifact[i] = fast_expo(fact[i], MOD - 2);
}
long long comb(long long x, long long y) {
  return mult(fact[x], mult(ifact[y], ifact[x - y]));
}
int main() {
  pre();
  cin >> n >> m;
  if (n == 2) {
    puts("0");
    return 0;
  }
  long long ans = 0;
  for (long long x = n - 1; x <= m; x++) {
    long long factor = mult(comb(x - 2, n - 3), fast_expo(2, n - 3));
    ans = add(ans, mult(x - 1, factor));
  }
  cout << ans << endl;
  return 0;
}
