#include <iostream>
#include <fstream>
using namespace std;
long long v[5000002], deq[5000002];

int main()
{
    int n, k;
    long long sum = 0;


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

    in >> n >> k;

    for (int i = 0; i < n; i++) {
        in >> v[i];
    }
    int left = 0;
    int right = -1;

    for (int i = 0; i < n; i++) {

        if (deq[left] <= i - k) {
            left++;
        }

        while (left <= right && v[deq[right]] >= v[i]) {
            right--;
        }

        deq[++right] = i;

        if (i+1 >= k) {
            sum += v[deq[left]];
        }
    }

    out << sum;
}