// Source: https://usaco.guide/general/io #include <bits/stdc++.h> using namespace std; using ll = long long; #define eb emplace_back int main() { ios::sync_with_stdio(0); cin.tie(0); ll n, t; cin >> n >> t; vector<ll> a(n); for (ll i{}; i < n; i++) cin >> a[i]; set<ll> cands; ll mn = *min_element(a.begin(), a.end()); ll mx = *max_element(a.begin(), a.end()); for (ll i{}; i < n; i++) { ll max_k = (mx - mn) / t + 10; for (ll k{}; k <= max_k; k++) { cands.insert(a[i] - k * t); } } ll ans = 1e18; for (ll x : cands) { ll unp = 0; for (ll i{}; i < n; i++) { ll dis; if (x >= a[i]) { dis = x - a[i]; } else { ll k = (a[i] - x) / t; ll d1 = abs(x - (a[i] - k * t)); ll d2 = abs(x - (a[i] - (k + 1) * t)); dis = min(d1, d2); } unp = max(unp, dis); } ans = min(ans, unp); } cout << ans << "\n"; }