CCC 2026 S1 Baby Hop, Giant Hop

    1#include <bits/stdc++.h>
    2using namespace std;
    3using ll = long long;
    4using i128 = __int128;
    5const int inf = 1e9;
    6const ll INF = 1LL << 60;
    7int main() {
    8    ios::sync_with_stdio(0); cin.tie(0);
    9    ll a, b, k, t; cin >> a >> b >> k >> t;
    10    if (t == 1) {
    11        if (b < a) swap(a, b);
    12        i128 s = (i128)(b - a) / k;
    13        ll ans1 = (b - a) % k + s;
    14        ll ans2 = (i128)(s + 1LL) * (i128)k - (b - a) + s + 1;
    15        cout << min(ans1, ans2) << '\n';
    16    } else {
    17        if (b < a) swap(a, b);
    18        i128 s = (i128)(b - a) / k;
    19        ll ans1 = (b - a) % k + s;
    20        ll ans2 = (i128)(s + 1LL) * (i128)k - (b - a) + s + 1;
    21        ll ans3 = (s >= 1 ? (i128)(b - a) - (i128)(s - 1LL) * (i128)k + (i128)(s - 1LL) : INF);
    22        ll best = min({b - a, ans1, ans2, ans3});
    23        ll ans = best + 2;
    24        for (ll x : {ans1, ans2, ans3, b - a}) {
    25            if (x > best) ans = min(ans, x);
    26        }
    27        cout << ans << '\n';
    28    }
    29    return 0;
    30}