#include <bits/stdc++.h>
using namespace std;

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

const int NMAX = 5000000;

int n, k;
long long a[NMAX + 2];

long long ans;
deque<int> dq;

int main()
{
    in >> n >> k;

    for(int i = 1; i <= n; i++)
        in >> a[i];

    dq.push_back(1);
    for(int i = 2; i <= n; i++)
    {
        while(!dq.empty() && dq.front() < i - k + 1)
            dq.pop_front();
        while(!dq.empty() && a[dq.back()] >= a[i])
            dq.pop_back();

        dq.push_back(i);

        if(i >= k)
            ans += a[dq.front()];
    }

    out << ans << '\n';
    return 0;
}