#include <bits/stdc++.h>
using namespace std;

int64_t solve(const int n, const int k, const vector<int> &A) {
  if (k == 1) return 0;

  int64_t sum = 0;
  __int128_t sum2 = 0;

  double min_var = 1e20;
  int min_var_idx = -1;

  for (int i = 0; i < n; i++) {
    sum += A[i];
    sum2 += 1LL * A[i] * A[i];

    // 範囲外に出たものを取り除く
    if (i >= k) {
      sum -= A[i-k];
      sum2 -= 1LL * A[i-k] * A[i-k];
    }
    if (i >= k - 1) {
      // k 要素の分散を求める
      double avg = 1.0 * sum / k;
      double variance = 1.0 * sum2 / k - avg * avg;
      if (min_var > variance) {
        min_var = variance;
        min_var_idx = i;
      }
    }
  }

  vector<int> B;
  for (int i = 0; i < k; i++) {
    B.emplace_back(A[min_var_idx - i]);
  }

  sort(B.begin(), B.end());

  int median = B[(k+1)/2-1];

  int64_t ans = 0;
  for (int b : B) {
    ans += abs(b - median);
  }

  return ans;
}

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);

  int n, k; cin >> n >> k;
  vector<int> A(n);
  for (int i = 0; i < n; i++) cin >> A[i];

  cout << solve(n, k, A) << endl;

  return 0;
}