#include <iostream>
#include <set>
#include <iterator>
#include <fstream>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

long long int rez = 0;
int n, k, a[5000000];
multiset <long long int> s;

int main()
{
    f >> n >> k;
    for (int i = 1;i <= n;i++){
        f >> a[i];
        if (i <= k)s.insert(a[i]);
        else{
            rez += *s.begin();
            //it = s.find(a[i-k]);
            s.erase(s.find(a[i-k]));
            s.insert(a[i]);
        }
    }
    rez += *s.begin();
    g << rez;
}