#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000;
int main(){
  int N, K;
  cin >> N >> K;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  if (K <= N - K){
    long long ans1 = 0, ans2 = 0;
    for (int i = 0; i < K; i++){
      ans1 += A[i] - A[0];
      ans2 += A[N - 1] - A[N - 1 - i];
    }
    for (int i = K; i < N; i++){
      ans1 -= A[i] - A[0];
      ans2 -= A[N - 1] - A[N - 1 - i];
    }
    cout << min(ans1, ans2) << endl;
  } else {
    vector<long long> S(N + 1);
    S[0] = 0;
    for (int i = 0; i < N; i++){
      S[i + 1] = S[i] + A[i];
    }
    long long ans = INF;
    for (int i = 0; i <= N - K; i++){
      long long p = (2 * K - N) / 2 + i * 2;
      long long x = A[p];
      long long tmp = 0;
      tmp += S[i] - S[0];
      tmp -= S[p] - S[i];
      tmp += S[i + K] - S[p];
      tmp -= S[N] - S[i + K];
      tmp += (N + p * 2 - i * 4 - K * 2) * x;
      ans = min(ans, tmp);
    }
    cout << ans << endl;
  }
}