/*
the author :
Luffy-san
"yazan sharba"
*/
#include <bits/stdc++.h>
using namespace std;
/*
⠀⠀⠀⠀⠀⠀⠀⠙⢦⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡠⠒⠁⠀⠀⠀⠀⠀⠘⢿⣆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⢷⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠓⠤⠤⠤⠤⠄⠒⠒⠉⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢻⣦⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⣻⣷⣄⡀⠀⠀⠀⠀⠀⠀⠀⠀
⠶⣦⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⢷⣦⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⡴⠟⠉⠀⠙⢿⣷⣦⣤⣀⣀⣀⡀⠄
⠀⠀⠙⢦⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠛⠿⢶⣤⣄⣀⡀⠀⠀⠀⣀⣀⣤⣤⡶⠟⠋⠀⠀⠀⠀⠀⠘⢿⣿⣿⠁⠀⠀⠀⠀
⠀⠀⠀⠀⢲⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣤⣾⠃⠀⠀⠀⠀⠀⠀⠀⠀⠈⠛⠻⣿⣶⣶⣿⡿⠿⠛⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⣿⡇⠀⠀⠀⠀
⠳⡄⠀⠀⣸⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣠⣤⣤⣷⣾⣿⠟⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣴⡿⠋⠉⠉⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢹⡇⠀⠀⠀⠀
⠀⢹⡀⢠⡟⠀⠀⠀⠀⠀⢀⣴⠀⠀⠀⠀⠀⢀⣴⡿⠋⠉⠹⣿⡿⠁⠀⠀⠀⠀⠀⠀⠀⠀⢀⣠⣴⣾⡿⠋⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⣷⠀⠀⠀⠀
⠀⢠⣿⡟⠀⠀⠀⠀⠰⣴⡿⠃⠀⠀⠀⠀⢠⣾⣿⣧⡀⠀⠀⣿⠁⠀⠀⠀⠀⠀⠀⢀⣠⣶⡟⣫⡽⠉⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢾⣧⠀⠀⠀
⣶⣿⡟⠀⠀⠀⠀⠀⣼⣿⠃⠀⠀⠀⠀⢠⣿⣿⢃⣿⣷⣄⢸⡟⠀⠀⠀⠀⠀⠀⣰⣿⣿⠿⠿⠿⣦⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣦⣿⡆⠀⠀
⠻⣿⠀⠀⠀⠀⠀⣼⣿⣿⠀⠀⠀⠀⣠⣾⣿⠿⠋⠁⠈⣻⣾⣧⠀⠀⠀⠀⢀⣾⣿⡟⠁⣀⠀⠀⠀⠹⣧⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣤⠿⠛⣿⡀⠀
⣶⣿⣦⣀⣀⣤⣾⣿⡟⢿⣇⡀⠀⢀⣿⣿⠋⠀⣠⣾⠟⣿⣿⣿⡀⠀⠀⠀⣸⡟⢻⡆⠈⢻⣿⠀⠀⢠⡿⠀⢰⡇⠀⠀⠀⠀⢀⣤⠶⢶⣄⠀⠀⠀⠀⠀⣠⡴⠟⠁⠀⠀⣿⡇⠀
⣿⠁⠉⠻⣿⣿⣿⡏⠁⠘⢿⣷⣶⣿⡿⠃⠀⠀⣿⣁⣶⣿⣿⣿⣇⡀⠀⣀⣿⣅⠈⠛⠷⠛⠁⠀⢀⣾⠇⢠⡾⠀⠀⠀⣠⡶⠋⠁⠀⠀⠹⣧⠀⢀⣴⠾⠋⠀⠀⢀⣤⣾⣿⡇⠀
⢿⡇⠀⠀⢻⣿⠇⠀⠀⠀⠈⣿⠟⠻⣇⠀⠀⠀⢿⣏⠻⣿⠏⢉⣿⣿⠿⠿⠿⢿⣦⣀⠀⣀⣠⣴⡿⢋⣴⠟⠁⠀⠀⣴⠟⠀⢠⣤⠀⠀⣰⣿⠿⠋⠁⠀⢀⣠⣴⡿⠟⢉⣿⡇⠀
⠈⠿⣶⣤⣼⣿⠀⠀⠀⠀⠀⠀⠀⠀⢻⣆⠀⠀⠈⢿⣿⣿⣾⠿⠛⠁⠀⠀⠀⢸⣿⣿⢿⣟⠿⠛⠛⠛⠁⠀⠀⠀⣸⣿⠀⠀⠙⢷⣶⠟⠋⠀⠀⣀⣤⣾⣿⡟⠁⠀⢺⣾⡿⠀⠀
⠉⠀⠈⠉⠃⣿⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⢷⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣾⠛⢻⣎⣿⠀⠀⠀⠀⠀⠀⢀⣴⣿⣿⣷⣤⣤⣤⣤⣴⣶⣾⣿⡋⠁⠀⢻⡇⠀⠀⣼⡟⠁⠀⠀
⣦⠀⠀⠀⠀⣿⡀⠀⠀⠀⠀⠀⣶⡀⠀⠀⠀⠙⠛⠶⣤⣄⣀⣀⣠⣤⡴⠾⠛⠁⠀⠈⠉⠙⠀⠀⠀⠀⠀⢠⣿⠟⠉⣿⠋⢹⣿⣏⣴⣿⣷⠞⣻⡟⠀⠀⢸⣷⣠⣼⠏⠀⠀⠀⠀
⢿⣿⣦⣤⣀⣿⡇⠀⠀⠀⢀⣴⠿⣷⣄⠀⠀⠀⠀⠀⠀⠈⠉⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣼⡟⠀⠀⣿⠀⠘⢿⣭⣛⣛⣛⣴⡿⠁⠀⠀⣸⣿⣿⠃⠀⠀⠀⠀⠀
⠀⠙⠻⣿⣿⣿⣧⠀⠀⠀⣸⡏⠀⠈⠻⣷⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡀⣿⠁⠀⠀⠹⣧⡀⠀⠉⠙⠛⠉⠁⠀⠀⣠⡾⠛⠛⣿⠀⠀⠀⠀⣠⡟
⠀⠀⠀⠀⠙⠿⣿⣷⡀⠀⣿⠁⠀⠀⠀⠈⢿⣷⣤⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡟⠀⣿⠀⠀⠀⠀⠈⠛⠶⠶⢤⡶⠶⠶⠿⠛⠁⠀⠀⠀⣿⣷⡶⠞⡩⠛⠀
⠀⠀⠀⠀⠀⠀⠘⠻⢿⣄⣿⡀⠀⠀⠀⢰⠟⠈⠙⠿⣷⣤⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠀⠀⠀⣃⣰⣿⠀⠀⢀⣤⣀⠀⠀⠀⠀⡀⠀⣀⣶⠶⠛⠀⠀⣼⣿⣿⠿⠋⢀⣠⠆
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⢿⣧⡀⠀⢀⡟⠀⠀⠀⠀⠈⠙⠻⢷⣦⣄⡀⠀⠀⠀⠀⠀⠀⠙⣷⣄⣴⣿⡿⠋⠀⠀⠀⠈⠙⠛⠛⠒⠲⣿⠛⠉⠁⠀⠀⢀⣾⠋⠉⠀⣀⣴⣿⡟⠃
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠙⣷⡄⣾⠁⠀⠀⠀⠀⠀⠀⢀⡾⠉⠙⠛⠿⣶⣦⣄⣀⠀⠀⠈⠛⠛⠡⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⣿⠀⠀⠀⠀⣰⣿⣃⣤⣶⠾⠛⠉⠁⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢿⣿⡄⠀⠀⠀⠀⠀⠀⡾⠀⠀⠀⠀⠀⠀⠈⢹⡟⠻⠷⠶⣤⣤⣤⣤⣤⣤⣤⣤⣤⣤⣤⣤⣴⠟⠁⠀⠀⢀⣼⣿⣿⠟⠉⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⣿⠿⣶⣄⠀⠀⠀⡼⠁⠀⠀⠀⠀⠀⠀⢀⡾⠁⠀⠀⠀⠀⣸⠋⠉⠈⠉⠉⣿⠉⠀⣠⠞⠁⠀⠀⠀⣀⣿⡿⠋⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⡇⠀⠙⠻⣦⣴⡃⠀⠀⠀⠀⠀⠀⢀⡾⠁⠀⠀⠀⠀⢰⡟⠀⠀⠀⠀⣸⢇⣠⠾⠉⠀⠀⠀⢀⣴⡿⠋⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢹⣷⡄⠀⠀⠠⣍⡛⠶⣤⣄⡀⠀⠀⡾⠁⠀⠀⠀⠀⢠⡟⠀⠀⠀⣀⣴⡿⠛⠁⠀⠀⠀⢀⣴⣿⠟⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠄⠒⠉⠁
⠱⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣾⣿⣿⣦⣀⠀⠀⠉⠒⠤⢍⣛⠳⠾⠷⢤⣤⣤⣤⣤⣾⣤⡴⠶⠟⠋⠁⠀⠀⠀⠀⢀⣴⣿⡿⠋⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠁⠀⠀⠀⠀
⠀⢣⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣿⣿⣿⣿⣷⣶⣤⣤⣀⣤⣄⣀⠀⠐⠒⠒⠂⠤⠤⠤⠄⠐⠀⠀⠀⢀⣀⣠⣴⣾⡿⢋⡿⠃⠀⠀⠀⠀⠀⠀⠀⠀⠐⠁⠀⠀⠀⠀⠀⠀
⠀⠀⠇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣯⠉⠛⠿⣿⣷⣍⠙⠻⣿⠿⠿⢿⣿⣷⣶⣿⣷⣶⣶⣶⣶⡶⣾⣿⣿⡿⢿⣿⣿⣶⣿⠃⠀⠀⠀⠀⠀⠀⠀⠀⠈⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢿⣿⣷⠀⠀⠈⠉⠛⠿⣦⣅⠀⠀⠀⠈⠉⠉⠉⠉⣿⣿⣿⣿⡷⠿⠋⠁⢀⣾⣿⡟⣿⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⣿⣿⡆⠀⠀⠀⠀⠀⠈⠙⢿⣦⡀⠀⠀⣀⣀⣤⣾⠿⠛⠁⠀⠀⠀⢠⣾⣷⠏⢸⣿⠃⠀⠀⠀⠀⠀⠀⠀⢰⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⡇⠠⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢹⣯⢿⣄⠀⠀⠀⠀⠀⠀⠀⠉⠻⣦⣀⣉⣽⠟⠁⠀⠀⠀⠀⠀⢠⣿⣿⠏⠀⣾⣿⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠈⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢹⣦⡙⢿⣶⣤⡄⠀⠀⠀⠀⠀⣀⡙⣓⡀⠀⠀⠀⠀⢀⣴⣴⣿⣿⠋⠀⠀⣿⡟⠀⠀⠀⠀⠀⠀⠀⠀⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
*/
#define yon(x) cout<<((x)?"YES\n":"NO\n");
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define ff first
#define ss second
#define em emplace
#define emp emplace_back
#define pb push_back
#define rep(i,j,k) for(int i=j;i<=k;i++)
#define per(i,j,k) for(int i=k;i>=j;i--)
#define forp(x,y,a) for(auto &[x,y]:(a))
#define mkp make_pair
typedef long long ll;
typedef pair<ll,ll> pll;
typedef vector<ll> vl;
typedef vector<pll> vpl;
typedef vector<vl> vvl;
typedef vector<vpl> vvpl;
typedef vector<string> vs;
typedef vector<set<ll> >vst;
typedef deque<ll> dl;
const ll inf =1e18+1;
const int N=1e6+1;
const ll dx[]={1,0,-1,0};
const ll dy[]={0,1,0,-1,0};
const ll mod=998244353;
const int LOG=31;
char dir[]={'D','R','U','L'};
void solve(){
ll n,t;
cin>>n>>t;
vl a(n);
rep(i,0,n-1) {
cin>>a[i];
a[i]%=t;
}
sort(all(a));
ll ans=inf;
ll lst=a[n-1];
rep(i,0,n-1) {
ans=min(ans,(lst-a[i]+1)/2);
lst=a[i]+t;
}
cout<<ans;
}
signed main(){
ios_base::sync_with_stdio(NULL);
cin.tie(nullptr);
cout.tie(nullptr);
#ifdef Usaco
string f="bphoto";
freopen((f+".in").c_str(),"r",stdin);
freopen((f+".out").c_str(),"w",stdout);
#endif
int t = 1;
//cin >> t;
while (t--) {
solve();
cout<<"\n";
}
}
/*
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣴⣿⣿⠀⠀⠀⢠⣾⣧⣤⡖⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⢀⣼⠋⠀⠉⠀⢄⣸⣿⣿⣿⣿⣿⣥⡤⢶⣿⣦⣀⡀
⠀⠀⠀⠀⠀⠀⠀⠀⣿⣿⡆⠀⠀⠀⣙⣛⣿⣿⣿⣿⡏⠀⠀⣀⣿⣿⣿⡟
⠀⠀⠀⠀⠀⠀⠀⠀⠙⠻⠷⣦⣤⣤⣬⣽⣿⣿⣿⣿⣿⣿⣿⣟⠛⠿⠋⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣴⠋⣿⣿⣿⣿⣿⣿⣿⣿⢿⣿⣿⡆⠀⠀
⠀⠀⠀⠀⣠⣶⣶⣶⣿⣦⡀⠘⣿⣿⣿⣿⣿⣿⣿⣿⠿⠋⠈⢹⡏⠁⠀⠀
⠀⠀⠀⢀⣿⡏⠉⠿⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⡆⠀⢀⣿⡇⠀⠀⠀
⠀⠀⠀⢸⣿⠀⠀⠀⠀⠀⠙⢿⣿⣿⣿⣿⣿⣿⣿⣿⣟⡘⣿⣿⣃⠀⠀⠀
⣴⣷⣀⣸⣿⠀⠀⠀⠀⠀⠀⠘⣿⣿⣿⣿⠹⣿⣯⣤⣾⠏⠉⠉⠉⠙⠢⠀
⠈⠙⢿⣿⡟⠀⠀⠀⠀⠀⠀⠀⢸⣿⣿⣿⣄⠛⠉⢩⣷⣴⡆⠀⠀⠀⠀⠀
⠀⠀⠀⠋⠀⠀⠀⠀⠀⠀⠀⠀⠈⣿⣿⣿⣿⣀⡠⠋⠈⢿⣇⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⠿⠿⠛⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀
*/
