#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define eb emplace_back
#define pu push
#define ins insert
#define fi first
#define se second
#define all(a) a.begin(),a.end()
#define bruh ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fu(x,a,b) for (auto x=a;x<=b;x++)
#define fd(x,a,b) for (auto x=a;x>=b;x--)
#define int ll
using namespace std;
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
/*
Competitive Programming notes that I need to study & fix my dumbass self:
1. Coding:
- Always be sure to check the memory of arrays (maybe use vectors), for loops
- Always try to maximize the memory if possible, even if you are going for subtasks
- Do not exploit #define int long long, it will kill you
2. Stress:
- Always try generating big testcases and try if they run
3. Time management:
- Don't overcommit or undercommit, always spend a certain amount of time to think a problem, don't just look at it and say I'm fucked
- Do not spend too much time coding brute-force solutions, they should be easily-codable solutions that don't take up too much time
Time management schedule:
Offline / LAH days (4 problems - 3h):
15' thinking of solution / idea
1. no idea: skip
2. yes idea: continue thinking for <= 15'
+ implementing: <= 20'
+ brute-force: <= 5'
+ test generator: <= 5'
I hate offline because I am dumb
*/
typedef pair<int, int> ii;
const int N = 5e5+5;
const int B = 750;
const int mod = 1e9+7;
const int inf = 1e18;
using cd = complex<double>;
const long double PI = acos(-1);
int power(int a,int b) {ll x = 1;if (a >= mod) a%=mod; while (b) {if (b & 1) x = x*a % mod;a = a*a % mod;b>>=1;}return x;}
int n,t;
int a[N];
int calc(int x)
{
int sum = -inf;
for (int i = 1; i <= n; i++)
{
if (a[i] <= x) sum = max(sum, x-a[i]);
else
{
int d = (a[i]-x) / t;
sum = max(sum, min({abs((a[i] - d*t) - x), abs((a[i] - (d+1)*t) - x), abs((a[i]-(d-1)*t) - x)}));
}
}
return sum;
}
void solve()
{
cin>>n>>t;
int mx = 0;
for (int i = 1; i <= n; i++) cin>>a[i], mx = max(mx, a[i]);
int l = 1, r = mx;
while (l < r-2)
{
int m1 = (2*l+r) / 3, m2 = (l+2*r) / 3;
if (calc(m1) <= calc(m2)) r = m2;
else l = m1;
}
// cout<<calc(15)<<endl;
// cout<<l<<" "<<r<<endl;
int res = inf;
for (int i = l; i <= r; i++) res = min(res, calc(i));
cout<<res;
}
/*
Go through the mistakes you usually make and revise your code, for god's sake...
*/
signed main()
{
bruh
//freopen("input.inp","r",stdin);
//freopen("output.inp","w",stdout);
solve();
}
