#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;


int main() {
    ifstream f("deque.in");

    int n, k, sum=0, size=0;
    int v2[100001];
    f>>n >>k;
    int v[100001];
    for (int i = 0; i < n; i++) {
        f >> v[i];
    }
    
    for (int i = 0; i < n; i++) {
        if (size > 0 && v2[0] <= i - k) {
            size--;
            for (int j = 0; j <size; j++) {
                v2[j] = v2[j + 1];
            }
        }
        while (size > 0 && v[v2[size - 1]] >= v[i]) {
            size--;
        }
        v2[size] = i;
        size++;
        if (i>= k - 1) {
            sum+= v[v2[0]];
        }
    }

    ofstream g("deque.out");
    g << sum;
    f.close();
    g.close();
    return 0;
}