#include <iostream> #include <vector> #include <string> #include <algorithm> #include <map> #include <set> #include <queue> #include <stack> #include <deque> #include <cmath> #include <climits> #include <cstring> #include <iomanip> #include <numeric> #include <functional> #include <bitset> #include <unordered_map> #include <unordered_set> #include <chrono> #include <random> using namespace std; typedef long long ll; typedef unsigned long long ull; typedef long double ld; #define rep(a,b) for(int a = 0;a<b;a++) #define st first #define nd second #define pb push_back #define all(a) a.begin(),a.end() const int inf = 1e9; const ll infl = 1e18; int main() { ios_base::sync_with_stdio(0); cin.tie(0); int n, t; cin >> n >> t; vector<int> a(n); rep(i, n){ cin>>a[i]; } rep(i, n){ a[i]%=t; } sort(all(a)); int w = abs(a[0] - a[n-1]); rep(i, n-1){ a[i]+=t; w = min(w, abs(a[i+1] - a[i])); } cout << w/2 << "\n"; return 0; }