#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];
a[i] %= k;
}
sort(begin(a), end(a));
vector<int> diffs;
for (int i = 1; i < n; ++i) {
diffs.push_back((a[i] - a[0]) % k);
}
sort(begin(diffs), end(diffs));
int res = INT_MAX;
for (int i = 1; i < n; ++i) {
int mndiff = (a[i - 1] - a[i] + k + 1) / 2;
res = min(res, mndiff);
}
//~ for (int i = 0; i < n; ++i) {
//~ a.back() -= k;
//~ sort(begin(a), end(a));
//~ int mndiif = (a.back() - a[0] + 1) / 2;
//~ res = min(res, mndiif);
//~ }
cout << res << "\n";
}
