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

using namespace std;

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

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

int main()
{
    f >> n >> k;
    for (int i = 1;i <= n;i++)f >> a[i];
    for (int i = 1;i <= k;i++)s.insert(a[i]);
    rez += *s.begin();
    for (int i = 2;i <= n - k + 1;i++){
        it = s.find(a[i-1]);
        s.erase(it);
        s.insert(a[i+k-1]);
        rez += *s.begin();
    }
    g << rez;
}