#include <algorithm>
#include <deque>
#include <fstream>
#include <iostream>
using namespace std;

deque<int> dq;
int a[5000005];

int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    int n, k;
    long long sum=0;
    cin >> n >> k;
    for (int i = 1; i <= n; ++ i) {
        cin >> a[i];
    }
    for (int i = 1; i <= n; ++ i) {
        while (!dq.empty() && a[dq.back()] >= a[i]) {
            dq.pop_back();
        }
        dq.push_back(i);
        if (dq.front() == i - k) {
            dq.pop_front();
        }
        if (i >= k) {
            sum += a[dq.front()];
        }
    }
    cout << sum << "\n";
    return 0;
}