#include <bits/stdc++.h>
using namespace std;
using LL=long long;
using ULL=unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)



int N,K;
LL A[200000];

LL solve(){
  LL ans=0;
  if(K*2<=N){
    rep(i,K) ans+=(A[i]-A[0])*2;
    rep(i,N) ans+=A[0]-A[i];
    return ans;
  }
  LL pibot = (N-K-K-1)/2;
  rep(i,pibot) ans+=(A[0]-A[i])*2;
  rep(i,K) ans+=(A[i]-A[0])*2;
  rep(i,N) ans+=A[0]-A[i];
  return ans;
}

int main(){
  scanf("%d%d",&N,&K);
  rep(i,N) scanf("%lld",&A[i]);
  LL ans=solve();
  reverse(A,A+N); rep(i,N) A[i]=-A[i];
  ans=min(ans,solve());
  printf("%lld\n",ans);
  return 0;
}