C++ :

#include <bits/stdc++.h>
using namespace std;
const int maxn = 4000400;

int n, m, t, maxt;
long long f[maxn], cnt[maxn];

int main() {
	cin >> n >> m;
	for (int i = 0; i < n; i ++) {
		cin >> t;
		cnt[t] ++;
		if (t > maxt) maxt = t;
	}
	for (int i = 0; i <= maxt + m; i ++) {
		long long tmp = 0;
		for (int j = 0; j < m && i-j >=0; j ++) {
			tmp += cnt[i-j] * ( (long long) j );
		}
		f[i] = tmp;
		if (i >= m) f[i] += f[i-m];
		for (int j = m+1; j <= 2*m && i - j >= 0; j ++) {
			tmp += cnt[i-j+1] * ( (long long) (j-1) );
			if (f[i-j] + tmp <= f[i]) f[i] = f[i-j] + tmp;
		}
	}
	long long ans=f[maxt];
	for(int i=1;i<=m;i++) 
	{
		ans=min(ans,f[maxt+i]);
	}
	cout<<ans<<endl;
	return 0;
}