# include <bits/stdc++.h>
# define ll long long
using namespace std;
const int MAXN = 5 * 1e5 + 1;
int n, t;
int a[MAXN];
void upgrade_speed()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
}
void read()
{
cin >> n >> t;
for(int i = 0; i < n; i++) cin >> a[i];
}
void small_case()
{
int minimum = 1e9, maximum = -1;
for(int i = 0; i < n; i++)
{
minimum = min(minimum, a[i] % t);
maximum = max(maximum, a[i] % t);
}
cout << maximum - minimum;
}
void solve()
{
if(t <= 2)
{
small_case();
return;
}
}
int main()
{
upgrade_speed();
read();
solve();
return 0;
}
