#include <bits/stdc++.h>
using namespace std;
using ll = long long; using pii = pair<ll,ll>;
const ll Nm = (1LL<<20); const ll E = 20;
ll pfs[Nm];
ll ipfs[Nm];
int main() {
ios_base::sync_with_stdio(false); cin.tie(0);
ll N,T; cin >> N >> T;
vector<ll> v0;
for (ll i=0;i<N;i++) {
ll a; cin >> a;
a = a%T;
v0.push_back(a);
v0.push_back(a+T);
}
sort(v0.begin(),v0.end());
for (ll i=0;i<(2*N);i++) {
ipfs[i]=v0[i];
//cout << v0[i] <<"\n";
}
pfs[0]=0;
for (ll i=0;i<(2*N);i++) {
pfs[i+1]=pfs[i]+ipfs[i];
}
ll ans = 8e18;
ll m = N/2; //median index
//i,i+1,i+2,...,i+m BELOW/AT
//i+m+1,i+m+2,...,i+N-1
for (ll i=0;i<=N;i++) {
// ll sum1 = pfs[i+m+1]-pfs[i];
// ll sum2 = pfs[i+N]-pfs[i+m+1];
// ll aval = (ipfs[i+m]*(m+1)-sum1)+(sum2-ipfs[i+m]*(N-m-1));
// ans = min(ans,aval);
ans = min(ans,(v0[i+N-1]-v0[i]+1)/2);
}
cout << ans << "\n";
}
