#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
#include <map>
#include <stack>
#include <bitset>
#include <string>
#include <cstring>
#include <iterator>
#include <random>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef long double ld;
const ll dim = 1e6+7;
//const ll mod = 1e9 + 7;
const ll inf = 1e18 + 77;
#define endl "\n"
#define fi first
#define pb push_back
#define se second
#define vll vector<ll>
ll n;
ll x;
ll a[dim];
int main() {
cin>>n>>x;
set<ll> s;
for(int i=1; i<=n; i++){
cin>>a[i];
a[i]=a[i]%x;
s.insert(a[i]);
}
ll mn=inf;
sort(a+1, a+1+n);
for(int i=1; i<=2*n; i++){
ll mxos=(*s.rbegin());
ll mnos=(*s.begin());
mn=min(abs(mxos-mnos), mn);
ll cur=(*s.begin());
s.erase(cur);
s.insert((x-cur));
}
cout<<(mn+1)/2<<endl;
return 0;
}
