#pragma comment(linker, "/STACK:1024000000,1024000000")

#include<cstdio>

#include<cstring>

#include<cmath>

#include<algorithm>

#include<vector>

#include<map>

#include<set>

#include<queue>

#include<stack>

#include<ctime>

#include<iostream>

using namespace std;

typedef long long LL;

const double pi=acos(-1.0),eps=1e-;

void File()

{

    freopen("D:\\in.txt","r",stdin);

    freopen("D:\\out.txt","w",stdout);

}

template <class T>

inline void read(T &x)

{

    char c = getchar();

    x = ;

    while(!isdigit(c)) c = getchar();

    while(isdigit(c))

    {

        x = x *  + c - '';

        c = getchar();

    }

}

int n,t;

long long x[],dp[],s[];

int q[],f1,f2;

bool delete1(int a,int b,int c)

{

    if(dp[b]-s[b]-x[b+]*(c-b)<=dp[a]-s[a]-x[a+]*(c-a)) return ;

    return ;

}

bool delete2(int a,int b,int c)

{

    if(

       ((dp[c]-s[c]+x[c+]*c)-(dp[b]-s[b]+x[b+]*b))*(x[b+]-x[a+]) <=

       ((dp[b]-s[b]+x[b+]*b)-(dp[a]-s[a]+x[a+]*a))*(x[c+]-x[b+])

         ) return ;

    return ;

}

int main()

{

    while(~scanf("%d%d",&n,&t))

    {

        for(int i=;i<=n;i++) scanf("%lld",&x[i]);

        sort(x+,x++n);

        for(int i=;i<=n;i++) s[i]=s[i-]+x[i];

        for(int i=t;i<*t;i++) dp[i]=s[i]-x[]*i;

        f1=f2=; q[]=; f2++; q[f2]=t;

        for(int i=*t;i<=n;i++)

        {

            while()

            {

                if(f2-f1+<) break;

                if(delete1(q[f1],q[f1+],i)) f1++;

                else break;

            }

            dp[i]=dp[q[f1]]+s[i]-s[q[f1]]-x[q[f1]+]*(i-q[f1]);

            while()

            {

                if(f2-f1+<) break;

                if(delete2(q[f2-],q[f2],i-t+)) f2--;

                else break;

            }

            f2++; q[f2]=i-t+;

        }

        printf("%lld\n",dp[n]);

    }

    return ;

}