/******************************************************************************

                              Online C++ Compiler.
               Code, Compile, Run and Debug C++ program online.
Write your code in this editor and press "Run" button to compile and execute it.

*******************************************************************************/

#include <fstream>
#include <algorithm>

using namespace std;



ifstream fin ("deque.in");
ofstream fout ("deque.out");

int main()
{
    int v[100], n,k;
    fin>>n>>k;
    for (int i=1; i<=n; i++){
        fin>>v[i];
    }
    int s=0, m;
    for (int i=1; i<=n-k+1; i++){
        m=v[i];
        for(int j=i+1; j<i+k; j++){
            m=min(m,v[j]);
        }
        s=s+m;
    }
    
    fout<<s;

    return 0;
}