#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
const ll MOD=1000000007;
ll n;
vector<ll> Tree;
vector<ll> Lazy;
vector<ll> lst;
void Build(ll index, ll start, ll end){
if(start==end){
Tree[index]=lst[start];
}
else{
ll mid=start+(end-start)/2;
Build(index+1,start,mid);
Build(index+2*(mid-start+1),mid+1,end);
Tree[index]=Tree[index+1]+Tree[index+2*(mid-start+1)];
}
}
void Push(ll index, ll start, ll end){
if(Lazy[index]!=0){
Tree[index]+=Lazy[index]*(end-start+1);
if(start!=end){
ll mid=start+(end-start)/2;
Lazy[index+1]+=Lazy[index];
Lazy[index+2*(mid-start+1)]+=Lazy[index];
}
}
Lazy[index]=0;
}
void Update(ll index, ll start, ll end, ll L, ll R, ll Value){
Push(index, start, end);
if(R<start or L>end){
return;
}
if(L<=start and end<=R){
Lazy[index]+=Value;
Push(index, start, end);
return;
}
ll mid=start+(end-start)/2;
Update(index+1,start,mid,L,R,Value);
Update(index+2*(mid-start+1),mid+1,end,L,R,Value);
Tree[index]=Tree[index+1]+Tree[index+2*(mid-start+1)];
}
ll Query(ll index, ll start, ll end, ll L, ll R){
Push(index,start,end);
if(R<start or L>end){
return 0;
}
if(L<=start and end<=R){
return Tree[index];
}
ll mid=start+(end-start)/2;
ll Left=Query(index+1,start,mid,L,R);
ll Right=Query(index+2*(mid-start+1),mid+1,end,L,R);
return Left+Right;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
ll n,t;
cin >> n >> t;
deque<ll> lst(n);
for(ll i=0;i<n;i++){
cin >> lst[i];
}
sort(lst.begin(),lst.end());
lst.erase(unique(lst.begin()+1,lst.end()),lst.end());
n=lst.size();
ll SmallestValue=lst[0];
for(ll i=1;i<n;i++){
ll Diff=abs(lst[i]-SmallestValue);
ll Multiplier=Diff/t;
ll Remainder=Diff%t;
lst[i]-=Multiplier*t;
if(Remainder>=t-Remainder){
lst[i]-=t;
}
}
sort(lst.begin(),lst.end());
ll mid=lst[0]+(lst[n-1]-lst[0])/2;
cout << max(abs(lst[0]-mid),abs(lst[n-1]-mid));
}
