#include <bits/stdc++.h>
#define int long long int
#define F first
#define S second
#define pb push_back
#define mp make_pair
#define pi pair<int, int>
#define INF 1e13
using namespace std;
int N, T, A[500010], mn = INF, hi = INF;
int32_t main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> N >> T;
for (int i = 0; i < N; i++) {
cin >> A[i];
mn = min(mn, A[i]);
}
for (int i = 0; i < N; i++) {
int m = (A[i] - mn) % T;
int d = min(m, T - m);
}
for (int i = mn - T / 2; i <= mn + T / 2; i++) {
int mxd = -INF;
for (int j = 0; j < N; j++) {
int m = (A[j] - i) % T;
int d = min(abs(m), abs(T - m));
mxd = max(mxd, d);
}
hi = min(hi, mxd);
}
cout << hi << "\n";
return 0;
}
