#include <fstream>
#define nmax 5000000
using namespace std;

int n,k,a[nmax],minim,suma;

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

int main()
{
    fin>>n>>k;
    for (int i=1;i<=n;i++)
        fin>>a[i];
    for (int i=1;i<=n;i++)
    {
        minim=999999999;
        for (int j=i;j<i+k;j++)
        {
            if (a[j]<minim)
                minim=a[j];
        }
        suma+=minim;
    }
    fout<<suma;
    return 0;
}