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

ifstream fin("deque.in");
ofstream fout("deque.out");
int v[5000001];
deque <int> dq;
int main()
{
    int n, k;
    fin >> n >> k;
    for (int i = 1; i <= n; i++)
        fin >> v[i];
    long long s = 0;
    for (int i = 1; i <= n; i++)
    {
        while (!dq.empty() && 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()];
    }
    fout << s;
    return 0;
}