#include <bits/stdc++.h>
using namespace std;
// #define int long long
#define FOR(i, a, b) for (int i = a; i <= (int)b; i++)
#define FORD(i, a, b) for (int i = a; i >= (int)b; i--)
#define MASK(i) (1LL << (i))
#define BIT(S, i) (((S) >> (i)) & 1)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
const int N = 5e5 + 5;
int n,k;
int a[N];
void init()
{
cin>>n>>k;
FOR(i,1,n) cin>>a[i];
}
namespace sub1
{
void solve()
{
int ans=2e9;
FOR(t,1,50000)
{
int ma=0;
FOR(i,1,n)
{
if(a[i]>=t)
{
int tam=(a[i]-t)/k;
int val=a[i] -k*tam;
int curma = abs(t-val);
tam++;
val=a[i]-k*tam;
curma=min(curma,abs(val-t));
tam--; tam--;
curma=min(curma,abs(val-t));
ma=max(ma,curma);
} else ma=max(ma,abs(t-a[i]));
}
ans=min(ans,ma);
}
cout << ans;
}
}
namespace sub2
{
int calc(int t)
{
int ma=0;
FOR(i,1,n)
{
if(a[i]>=t)
{
int tam=(a[i]-t)/k;
int val=a[i] -k*tam;
int curma = abs(t-val);
tam++;
val=a[i]-k*tam;
curma=min(curma,abs(val-t));
tam--; tam--;
curma=min(curma,abs(val-t));
ma=max(ma,curma);
} else ma=max(ma,abs(t-a[i]));
}
return ma;
}
void solve()
{
int l=0,r=1e9,ans=2e9;
FOR(time,1,50)
{
int mid1 = l + (r-l)/3;
int mid2 = r - (r-l)/3;
int cost1 = calc(mid1);
int cost2 = calc(mid2);
ans=min(ans,cost1); ans=min(ans,cost2);
if(cost1 >= cost2)
{
l=mid1;
} else r=mid2;
}
cout << ans;
}
}
void process()
{
// sub1::solve();
sub2::solve();
}
signed main(void)
{
ios_base::sync_with_stdio(false); cin.tie(nullptr);
#define taskname "kieuoanh"
if(fopen(taskname".inp", "r"))
{
freopen(taskname".inp", "r", stdin);
freopen(taskname".out", "w", stdout);
}
init();
process();
return 0;
}
