#include <iostream>
#include <vector>
#include <fstream>
#include <deque>
#define cin f
#define cout g
#define int long long
using namespace std;

int k;

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

int main() {
    ios::sync_with_stdio(false);

    deque<int> dq;

    int n;
    int s = 0;

    cin >> n >> k;
    vector<int> v(n + 1);
    for (int i = 1; i <= n; i++) {
        cin >> v[i];
    }
    for (int i = 1; i <= n; i++) {
        if (i >= k && dq.front() == i - k)
            dq.pop_front();
        while (!dq.empty() && v[dq.back()] > v[i]) {
            dq.pop_back();
        }
        dq.push_back(i);
        if (i >= k)
            s += v[dq.front()];
    }
    cout << s;
    return 0;
}