#include <bits/stdc++.h> using namespace std; #define endl "\n" #define int long long #define pii pair<int, int> #define ff first #define ss second #define entire(x) (x).begin(), (x).end() const int inf = 1e16; int32_t main(){ ios::sync_with_stdio(false); cin.tie(nullptr); int n, k; cin >> n >> k; vector<int> a(n); for (int i = 0; i < n; i++) cin >> a[i], a[i] %= k; // int ans = inf; // for (int cur = 0; cur < k; cur++){ // int cmax = 0; // for (auto t : a){ // cmax = max(cmax, min((k - t + cur) % k, k - ((k - t + cur) % k))); // } ans = min(ans, cmax); // } // cout << ans << endl; int diff = max(a[0], a[1]) - min(a[0], a[1]), ans = (min(diff, k - diff) + 1) / 2; cout << ans << endl; return 0; }