[CSES] Ferris Wheel

void solve() {
    ll n, x;
    cin >> n >> x;

    map<ll, ll> mp;
    rep(i, n) {
        ll xx;
        mp[xx]++;
    }

    ll ans = 0;
    while (sz(mp)) {
        auto it_min = mp.begin();
        auto it_mx = mp.upper_bound(x - it_min->f);

        if (--it_mx != mp.begin()) {
            // exist
            if (it_mx->f == it_min->f) {
                // same 
                if (it_mx->s > 1) {
                    mp[it_mx->f]--;
                }
            }
            else {
                mp[it_mx->f]--;
            }


            if (mp[it_mx->f] == 0) {
                mp.erase(it_mx);
            }
        }

        ans++;
        mp[it_min->f]--;
        if (mp[it_min->f] > 0) mp.erase(it_min);
    }

    cout << ans << "\n";

}