#include <iostream>

#include <deque>
#include <fstream>

using namespace std;

const int NMAX = 5000005;
int n, k, v[NMAX];
deque <int> dq;

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