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

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

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

    deque<long long> dq;

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