#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<long long, long long>;
#define pb push_back
#define ins insert
#define fi first
#define se second
#define btpc __builtin_popcount
#define btclz __builtin_clz
#define sz(x) (int)(x.size());
#define all(x) x.begin(), x.end()
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};
template<class X, class Y>
bool minimize(X &x, const Y &y) {
if (x > y)
{
x = y;
return true;
}
return false;
}
template<class X, class Y>
bool maximize(X &x, const Y &y) {
if (x < y)
{
x = y;
return true;
}
return false;
}
const int MOD = 1e9 + 7; //998244353
/* Author : Le Ngoc Bao Anh, A5K37 Le Quy Don High School for Gifted Student, Da Nang */
/* University of Wollongong */
const long long INF = 1e9;
const int N = 1e6 + 10;
ll pref[N], a[N];
void BaoJiaoPisu() {
int n; cin >> n;
ll T; cin >> T;
for(int i = 1; i <= n; i++) {
cin >> a[i];
a[i] %= T;
}
sort(a + 1, a + 1 + n);
ll ans = 1e18;
for(int i = 1; i <= n; i++) a[i + n] = a[i] + T;
for(int i = 1; i <= 2 * n; i++) pref[i] = pref[i - 1] + a[i];
for(int i = 0; i <= n; i++) {
ll res = 0;
int l = i + 1;
int r = n + i;
minimize(ans, (a[r] - a[l] + 1) / 2);
}
cout << ans;
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifndef ONLINE_JUDGE
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
#else
//online
#endif
int tc = 1, ddd = 0;
// cin >> tc;
while(tc--) {
//ddd++;
//cout << "Case #" << ddd << ": ";
BaoJiaoPisu();
}
}
