#include<bits/stdc++.h>

using namespace std;

#define setIO(s) freopen(s".in","r",stdin)

#define maxn 200000

#define inf 10000000000000

#define get(x) (ch[f[x]][1]==x)

#define ll long long

int root,cc,kk;

int h[maxn],ch[maxn][2],f[maxn],siz[maxn],val[maxn];

long long sumv[maxn];

long long ans=inf;

void pushup(int x)

{

    sumv[x]=sumv[ch[x][0]]+sumv[ch[x][1]]+h[x];

    siz[x]=siz[ch[x][0]]+siz[ch[x][1]]+1;

}

void rotate(int x)

{

    int old=f[x],fold=f[old],which=get(x);

    ch[old][which]=ch[x][which^1],f[ch[old][which]]=old;

    ch[x][which^1]=old,f[old]=x,f[x]=fold;

    if(fold) ch[fold][ch[fold][1]==old]=x;

    pushup(x),pushup(old);

}

void splay(int x,int &tar)

{

    int u=f[tar];

    for(int fa;(fa=f[x])!=u;rotate(x))

        if(f[fa]!=u)

            rotate(get(fa)==get(x)?fa:x);

    tar=x;

}

void insert(int &x,int key,int ff)

{

    if(!x) x=key,f[x]=ff;

    else insert(ch[x][h[key]>h[x]],key,x);

    pushup(x);

}

int query(int kth)

{

    int x=root;

    while(1)

    {

        if(siz[ch[x][0]]+1==kth) return x;

        if(siz[ch[x][0]]>=kth) x=ch[x][0];

        else kth-=(siz[ch[x][0]]+1),x=ch[x][1];

    }

}

void del(int x)

{

    if(!ch[x][0]) root=ch[x][1], f[root]=ch[x][1]=0;

    else if(!ch[x][1]) root=ch[x][0], f[root]=ch[x][0]=0;

    else

    {

        int l=ch[x][0];

        while(ch[l][1]) l=ch[l][1];

        splay(l, ch[x][0]);

        ch[l][1]=ch[x][1], f[ch[x][1]]=l, f[l]=ch[x][0]=ch[x][1]=0, pushup(l);

        root=l;

    }

}

void solve(int k,int L)

{

    int mid=(k%2==0)?k/2:(k/2)+1,x=query(mid);

    splay(x,root);

    int l=ch[root][0],r=ch[root][1];

    ll re=0;

    re+=(h[x]*siz[l]-sumv[l]);

    re+=(sumv[r]-h[x]*siz[r]);

    if(re<ans) ans=re, cc=L, kk=h[x];

}

int main()

{

    // setIO("input");

    int n,k,i,j;

    scanf("%d%d",&n,&k);

    for(i=1;i<=n;++i) scanf("%d",&h[i]);

    for(i=1;i<=k;++i) { insert(root,i,0); if(i%6==0) splay(i,root); }

    solve(k,1);

    for(i=k+1;i<=n;++i)

    {

        j=i-k+1;

        splay(j-1, root), del(j-1), insert(root,i,0), splay(i,root),  solve(k,j);

    }

    printf("%lld\n",ans);

    return 0;

}