#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int,int>
#define pb push_back
#define fi first
#define se second
#define dd(x) cout<<#x<<" is "<<x<<endl;
signed main(){
ios::sync_with_stdio(0); cin.tie(0);
int n,t; cin>>n>>t;
int A[n];
int mi = LLONG_MAX;
for(int i=0; i<n; i++) cin>>A[i], mi = min(mi,A[i]);
//int h=0,l=0;
int ans = LLONG_MAX;
for(int i=0; i<=t; i++){
int h=0;
for(int j=0; j<n; j++){
int a = mi-i, b = A[j];
int d = abs(a-b);
int k = d%t;
k = min(k,t-k);
h = max(h,k);
//l = max(l,t-k);
}
ans = min(ans,h);
}
//dd(h) dd(l)
//cout<<min((h+1)/2, (l+1)/2);
cout<<ans;
return 0;
}
