#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];
ll check(ll md){
ll mn1=0;
for(int i=1; i<=n; i++){
mn1=max(mn1, min(abs(x-a[i]-md)%x, abs(a[i]-md)%x));
}
return mn1;
}
int main() {
cin>>n>>x;
for(int i=1; i<=n; i++){
cin>>a[i];
a[i]=a[i]%x;
}
sort(a+1, a+1+n);
ll mn1=0;
ll mn2=0;
ll ans=inf;
ll l=0;
ll r=x-1;
while((r-l)>=3){
ll m1=l+(r-l)/3;
ll m2=r-(r-l)/3;
if(check(m1)<check(m2)){
r=m2-1;
}
else{
l=m1;
}
}
cout<<min({check(l), check(l+1), check(l+2), check(l+3)})<<endl;
return 0;
}
