#include<bits/stdc++.h> usingnamespace std; #define ll long long constint N = 2e5 + 10; constint INF = 0x3f3f3f3f; const ll mod = 998244353; ll ans; ll n, m; ll P[N]; ll Pow(ll a, ll b){ ll res = 1; while (b) { if (b & 1)res = res * a%mod; a = a * a%mod; b >>= 1; } return res; } ll C(ll n, ll k){ return P[n] * Pow(P[k], mod - 2) % mod*Pow(P[n - k], mod - 2) % mod; } intmain(){ cin >> n >> m; P[0] = 1; for (ll i = 1; i <= max(n, m); i++)P[i] = P[i - 1] * i%mod; if (m < n - 1) { puts("0"); return0; } ans = C(m, n - 1); ll tmp = 0; for (ll i = 0; i <= n - 2; i++) { tmp = (tmp + C(n - 2, i)) % mod; } ans = ans * tmp%mod*Pow(2, mod - 2) % mod; ans = ans * (n - 2) % mod; cout << ans << endl; return0; }