#include <iostream>
#include <vector>
#include <climits>
#include <cmath>
using namespace std;
int n, t;
vector<int> v;
int max_discomfort(int x) {
int max_d = 0;
for (int i = 0; i < v.size(); i++) {
int k = max(0, (int)floor((double)(v[i] - x) / t + 0.5));//optimal jacket count
int temp = v[i] - k*t;
max_d = max(max_d, abs(x - temp));
}
return max_d;
}
int main() {
//ans = sum of modulo?
int mx = 0, mn = INT_MAX;
cin >> n >> t;
v.resize(n);
for (int i = 0; i < n; i++) {
cin >> v[i];
mx = max(mx, v[i]);
mn = min(mn, v[i]);
}
//ternery search
int l = 0, r = mx;
while (r - l > 2) {
int m1 = l + (r - l)/3;
int m2 = r - (r - l)/3;
if (max_discomfort(m1) < max_discomfort(m2)) r = m2;
else l = m1 + 1;
}
int ans = INT_MAX;
for (int i = l; i <= r; i++) ans = min(ans, max_discomfort(i));
cout << ans << endl;
}
