#include<iostream>
#include<fstream>
#include<climits>
#include<cmath>

using namespace std;

int dp[100005];

int main()
{
    ifstream input("walk.in");
    ofstream output("walk.out");

    int n,k;
    int a[100005];

    int min_time = INT_MAX;

    input >> n >> k;
    for(int i = 0;i<n;i++)
        input >> a[i];

    dp[0] = abs(a[1] - a[0]);
    for(int i = 1;i<n;i++)
        dp[i] = dp[i-1] + abs(a[i-1]-a[i]);

    min_time = dp[k-2];
    for(int i = k-1;i<n;i++)
        if(dp[i]-dp[i-k+1]<min_time) min_time = dp[i]-dp[i-k+1];

    output << min_time << endl;
}