#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

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

    int N, K;
    cin >> N >> K;
    vector<ll> A(N), S(N + 1);
    for(int i = 0; i < N; ++i){
        cin >> A[i];
        S[i + 1] = S[i] + A[i];
    }

    ll ans = 8e+18;
    int l = 0;
    for(int i = 0; i < N; ++i){
        ll sum = -(A[i] * l - S[l]);
        sum += A[i] * (i - l) - (S[i] - S[l]);
        sum += (S[l + K] - S[i]) - A[i] * (l + K - i);
        sum -= (S[N] - S[l + K]) - A[i] * (N - (l + K));
        chmin(ans, sum);
        while(l + K < N && abs(A[i + 1] - A[l]) > abs(A[i + 1] - A[l + K])){
            ++l;
        }
    }

    cout << ans << endl;

    return 0;
}