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

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

deque <int> d;
const int NMAX = 5000003;
int v[NMAX];
long long s;
int main()
{
    int n, k;
    cin >> n >> k;
    for (int i = 1; i <= n; i++)
    {
        cin >> v[i];
        if (!d.empty() and d.front() == i - k)
            d.pop_front();
        while (!d.empty() and v[d.back()] >= v[i])
            d.pop_back();
        d.push_back(i);
        if (i >= k)
            s += v[d.front()];
    }
    cout << s;
}