#include <iostream>
#include <deque>
#include <fstream>

using namespace std;


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

int n, k, a, v[5000000], s=0, minim;
deque <int> deq;

void citire ()
{
    fin >> n >> k;
    for(int i=0; i<n; i++)
        v[i] = 0;
    int i=0;
    while (fin >> a)
    {
        v[i] = a;
        i++;
    }
}

void initializare ()
{
    for(int i=0; i<k; i++)
        deq.push_back(v[i]);
}

int aflare_minim ()
{
    minim = deq.front();
    for(int i=0; i<k; i++)
        if(deq[i]<minim)
            minim = deq[i];
    return minim;
}

void prelucrare ()
{
    for (int i=k; i<=n; i++)
    {
        s += aflare_minim();
        deq.push_back(v[i]);
        deq.pop_front();
    }
}

int main()
{
    citire();
    initializare();
    prelucrare();
    fout << s;
    return 0;
}