// Source: https://usaco.guide/general/io #include <bits/stdc++.h> using namespace std; using ll = long long; #define eb emplace_back vector<ll> a; ll n, t; ll calc(ll x){ ll mx_dis = 0; for (ll i{}; i < n; i++) { ll dis; if (x >= a[i]) { dis = x - a[i]; } else { ll k = (a[i] - x) / t; dis = min(abs(x - (a[i] - k * t)), abs(x - (a[i] - (k + 1) * t))); } mx_dis = max(mx_dis, dis); } return mx_dis; } int main() { ios::sync_with_stdio(0); cin.tie(0); cin >> n >> t; a.resize(n); for (ll i{}; i < n; i++) cin >> a[i]; ll ans = 1e18; for (ll k1{}; k1 <= 2000; k1++) { for (ll k2{}; k2 <= 2000; k2++) { ll p1 = a[0] - k1 * t; ll p2 = a[1] - k2 * t; ans = min(ans, calc(p1)); ans = min(ans, calc(p2)); ll mid = (p1 + p2) / 2; ans = min(ans, calc(mid)); ans = min(ans, calc(mid + 1)); } } cout << ans << "\n"; }