#include <bits/stdc++.h>
#define For(i, a, b) for (int(i) = (int)(a); (i) < (int)(b); ++(i))
#define rFor(i, a, b) for (int(i) = (int)(a)-1; (i) >= (int)(b); --(i))
#define rep(i, n) For((i), 0, (n))
#define rrep(i, n) rFor((i), (n), 0)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef unsigned long long ulint;
typedef pair<int, int> pii;
typedef pair<lint, lint> pll;
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
T div_floor(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a >= 0 ? a / b : (a + 1) / b - 1;
}
template <class T>
T div_ceil(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a > 0 ? (a - 1) / b + 1 : a / b;
}

constexpr lint mod = 1000000007;
constexpr lint INF = mod * mod;
constexpr int MAX = 200010;

int main() {
    int n, K;
    scanf("%d%d", &n, &K);
    lint a[n], asum[n + 1];
    asum[0] = 0;
    rep(i, n) scanf("%lld", &a[i]), asum[i + 1] = asum[i] + a[i];

    int l = 0, r = K;
    lint ans = INF;
    rep(i, n) {
        while (r < n && a[r] - a[i] < a[i] - a[l]) {
            ++r;
            ++l;
        }
        lint tmp = a[i] * (n - r + i - l);
        tmp -= a[i] * (r - i + l);
        tmp += asum[r] - asum[i] + asum[l];
        tmp -= asum[n] - asum[r] + asum[i] - asum[l];
        chmin(ans, tmp);
    }

    printf("%lld\n", ans);
}