#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, k;
cin >> n >> k;
vector<int> a(n);
for (int i = 0; i < n; ++i) {
cin >> a[i];
}
auto get_min = [&](int t) -> int {
int res = 0;
for (int i = 0; i < n; ++i) {
int now = a[i] + t;
for (int j = 0; j < 100; ++j) {
now = min(now, abs(t - (a[i] - j * k)));
}
res = max(res, now);
}
return res;
};
int res = INT_MAX;
for (int T = 0; T <= 10; ++T) {
for (int j = 1; j <= k; ++j) {
res = min(res, get_min(j + T * k));
//~ cout << get_min(j + T * k) << " ";
}
//~ cout << "\n";
}
//~ cout << "\n";
cout << res << "\n";
}
