//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,sse,sse2,sse3,ssse3,sse4,abm,popcnt,mmx")
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef double db;
typedef long double ldb;
typedef complex<double> cd;

constexpr ll INF64 = 9'000'000'000'000'000'000, INF32 = 2'000'000'000, MOD = 1'000'000'007;
constexpr db PI = acos(-1);
constexpr bool IS_FILE = false, IS_TEST_CASES = false;

random_device rd;
mt19937 rnd32(rd());
mt19937_64 rnd64(rd());

template<typename T>
bool assign_max(T& a, T b) {
	if (b > a) {
		a = b;
		return true;
	}
	return false;
}

template<typename T>
bool assign_min(T& a, T b) {
	if (b < a) {
		a = b;
		return true;
	}
	return false;
}

template<typename T>
T square(T a) {
	return a * a;
}

template<>
struct std::hash<pair<ll, ll>> {
	ll operator() (pair<ll, ll> p) const {
		return ((__int128)p.first * MOD + p.second) % INF64;
	}
};

void solve() {
	ll n, t;
	cin >> n >> t;
	deque<ll> arr(n);
	for (ll i = 0; i < n; i++) {
		cin >> arr[i];
		arr[i] = arr[i] % T;
	}
	sort(arr.begin(), arr.end());
	ll ans = INF32;
	for (ll i = 0; i < n; i++) {
		assign_min(ans, (arr.back() - arr.front() + 1) / 2);
		arr.push_front(arr.back() - T);
		arr.pop_back();
	}
	cout << ans << '\n';
}

int main() {
	if (IS_FILE) {
		freopen("", "r", stdin);
		freopen("", "w", stdout);
	}
    	ios_base::sync_with_stdio(false);
    	cin.tie(0);
    	cout.tie(0);
	ll t = 1;
	if (IS_TEST_CASES) {
		cin >> t;
	}
	for (ll i = 0; i < t; i++) {
		solve();
	}
}

answer.code: In function ‘void solve()’:
answer.code:56:35: error: ‘T’ was not declared in this scope
   56 |                 arr[i] = arr[i] % T;
      |                                   ^
answer.code:62:45: error: ‘T’ was not declared in this scope
   62 |                 arr.push_front(arr.back() - T);
      |                                             ^
answer.code: In function ‘int main()’:
answer.code:70:24: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   70 |                 freopen("", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~
answer.code:71:24: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   71 |                 freopen("", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~