#include <bits/stdc++.h>
#include <experimental/random>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
//using namespace __gnu_pbds;
void solve1();
using ll = long long;
using ull = unsigned long long;
using ld = long double;
#define int long long
const int INF = 1e18;
const int MOD = 1e9 + 7;
signed main() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int qwerty = 1;
// cin >> qwerty;
while (qwerty--) {
solve1();
}
}
void solve1() {
int n, t;
cin >> n >> t;
int mn = INF, mx = -1;
for (int i = 0; i < n; i++) {
int x;
cin >> x;
x %= t;
mn = min(mn, x);
mx = max(mx, x);
}
int fir = (mn + mx) / 2;
int sec = (mn + mx - t) / 2;
int f = max(abs(mn - fir), abs(mx - fir));
int s = max(abs(mn - sec), abs(mx - t - sec));
if (f < s) {
cout << fir;
} else {
cout << sec;
}
}
