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#include <iostream>
#include <deque>
#include <fstream>
#include <vector>
#include <limits.h>
using namespace std;
int main()
{
    ifstream f("vila2.in");
    ofstream g("vila2.out");
    int n,k;
    f>>n>>k;
    
    vector<int> a(n);
    deque<int> dq_min;
    deque<int> dq_max;
    
    for(int i=0; i<n; i++)
    {
        f>>a[i];
    }
    
    int dif_max=INT_MIN;
    int mini,maxi;
    for(int i=0; i<n; i++)
    {
        if(!dq_min.empty() && a[dq_min.back()]>=a[i])
        {
            dq_min.pop_back();
        }
        if(!dq_max.empty() && a[dq_max.back()]<=a[i])
        {
            dq_max.pop_back();
        }
        
        dq_min.push_back(i);
        dq_max.push_back(i);
        
        if(dq_min.front() < i-k)
        {
            dq_min.pop_front();
        }
        if(dq_max.front() < i-k)
        {
            dq_max.pop_front();
        }
        
        if(dq_max.back()-dq_min.back()<=k-1)
        {
            int dif=a[dq_max.front()]-a[dq_min.front()];
            if(dif>dif_max)
            {
                dif_max=dif;
            }
        }
    }
    g<<dif_max;
    return 0;
}