#include <bits/stdc++.h>
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");
int main() {
 
    int n, k;
    fin >> n >> k;

    vector<int> v(n+1);
    deque<int> slidingWindow;
    long long sumaMinime = 0;
    for(int i = 1; i <= n; i++)
    {
        fin >> v[i];
        while(!slidingWindow.empty() && v[i] < v[slidingWindow.back()])
        {
            slidingWindow.pop_back();
        }
        slidingWindow.push_back(i);

        if(i >= k) ///inseamna ca deja am o secv intreaga de k elem
        {
            if(slidingWindow.front() <= i - k)
            {
                slidingWindow.pop_front();
            }
            sumaMinime += v[slidingWindow.front()];
        }
    }
    fout << sumaMinime;
    return 0;
}