// 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";
}
