#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#include<random>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (int)(Y);++(X))
#define reps(X,S,Y) for (int (X) = (int)(S);(X) < (int)(Y);++(X))
#define rrep(X,Y) for (int (X) = (int)(Y)-1;(X) >=0;--(X))
#define rreps(X,S,Y) for (int (X) = (int)(Y)-1;(X) >= (int)(S);--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())
#define Endl endl
#define NL <<"\n"
#define cauto const auto

using namespace std;
using ll=long long;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
template<class T> using vv=vector<vector<T>>;
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
//#undef NUIP
#ifdef NUIP
#include "benri.h"
#else
#define out(args...)
#endif
void ouT(ll x,int d=3){auto re=to_string(x);if((int)re.size()>d) re=x>0?"oo":"-oo";cout<<string(d-re.size(),' ')<<re<<",";}
#ifdef __cpp_init_captures
template<typename T>vector<T> table(int n, T v){ return vector<T>(n, v);}
template <class... Args> auto table(int n, Args... args){auto val = table(args...); return vector<decltype(val)>(n, move(val));}
#endif
template<class A,class B> pair<A,B> operator+(const pair<A,B> &p,const pair<A,B> &q){ return {p.X+q.X,p.Y+q.Y};}
template<class A,class B,class C,class D> pair<A,B>& operator+=(pair<A,B> &p,const pair<C,D> &q){ p.X+=q.X; p.Y+=q.Y; return p;}
template<class A,class B> pair<A,B> operator-(const pair<A,B> &p,const pair<A,B> &q){ return {p.X-q.X,p.Y-q.Y};}
template<class A,class B,class C,class D> pair<A,B>& operator-=(pair<A,B> &p,const pair<C,D> &q){ p.X-=q.X; p.Y-=q.Y; return p;}
template<class A,class B> istream& operator>>(istream &is, pair<A,B> &p){ is>>p.X>>p.Y; return is;}
template<class T=ll> T read(){ T re; cin>>re; return move(re);}
template<class T=ll> T read(const T &dec){ T re; cin>>re; return re-dec;}
template<class T=ll> vector<T> readV(const int sz){ vector<T> re(sz); for(auto &x:re) x=read<T>(); return move(re);}
template<class T=ll> vector<T> readV(const int sz, const T &dec){ vector<T> re(sz); for(auto &x:re) x=read<T>(dec); return move(re);}
vv<int> readG(const int &n,const int &m){ vv<int> g(n); rep(_,m){ cauto a=read<int>(1),b=read<int>(1); g[a].pb(b); g[b].pb(a);} return move(g);}
vv<int> readG(const int &n){ return readG(n,n-1);}
#define TT cauto TTT=read();rep(_,TTT)
const ll MOD=1e9+7; //998244353;

int main(){
  ios_base::sync_with_stdio(false); cin.tie(0);
  cout<<fixed<<setprecision(0);
	cauto n=read(0);
	cauto t=read(0);
	cauto vs=readV(n);
	ll re=1e18;
	rep(posL,n+1-t){
		cauto posR=posL+t;
		cauto sum=[&](int i){ return -min(i,posL)+max(0,min(i,posR)-posL)-max(0,i-posR);};
		cauto eval=
			[&](ll x){
				ll re=0;
				rep(i,n){
					if(i<posL || i>=posR) re-=abs(x-vs[i]);
					else re+=abs(x-vs[i]);
				}
				out(posL,posR,x,re,1);
				return re;
			};
		int l=posL,r=posR;
		if(l) --l;
		if(r==n) --r;
		while(r-l>4){
			cauto m=(l+r)/2;
			// out(m,eval(m+1),eval(m),sum(m+1),(vs[m+1]-vs[m])*(sum(m+1)-(t-(n-t)-sum(m+1))),1);
			// assert(eval(m+1)-eval(m)==(vs[m+1]-vs[m])*(sum(m+1)-(t-(n-t)-sum(m+1))));
			(eval(vs[m+1])-eval(vs[m])<0?l:r)=m;
		}
		reps(i,l,r+1) MN(re,eval(vs[i]));
		MN(re,eval(vs[posL]));
		MN(re,eval(vs[max(0,posR-1)]));
		MN(re,eval(vs[0]));
		MN(re,eval(vs[n-1]));
	}
	cout<<re NL;
  return 0;
}