#include <bits/stdc++.h>
using namespace std;
using lint = long long;
struct fast_ios { fast_ios(){ cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define REP(i, n) FOR(i,0,n)


int main() {
    int N, K;
    cin >> N >> K;
    vector<lint> A(N);
    for (auto &a : A) cin >> a;
    vector<lint> cum(N + 1);
    REP(i, N) cum[i + 1] = cum[i] + A[i];
    lint ret = 1LL << 60;

    int l = 0, r = K;
    REP(m, N) {
        if (m == r) l++, r++;
        while (r < N and abs(A[m] - A[l]) > abs(A[m] - A[r])) l++, r++;
        lint tmp = A[m] * (m - l) - (cum[m] - cum[l]) + (cum[r] - cum[m]) - A[m] * (r - m);
        tmp -= (cum[N] - cum[r]) - A[m] * (N - r) + A[m] * l - cum[l];
        ret = min(ret, tmp);
    }
    cout << ret << '\n';
}