#include <fstream>
using namespace std; 

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

int valori[5000001], deque[5000001];

int main()
{
    int nrValori, lungimeK; 
    fin >> nrValori >> lungimeK; 


    for (int i = 1; i <= nrValori; i++)
        fin >> valori[i]; 

    int suma = 0;
    for (int i = 1; i <= nrValori - lungimeK + 1; i++)
    {
        deque[i] = i;

        for (int k = 1; k < lungimeK; k++)
        {
            if (valori[deque[i]] > valori[i + k])
                deque[i] = i + k;
        }

        suma += valori[deque[i]];
    }

    fout << suma;
    

}