#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

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

int n, k;
deque <int> dq; //pozitiile el
int a[5000002];
long long ans;

int main()
{
    f >> n >> k;
    for (int i = 1; i <= n; i++)
        f >> a[i];
    for (int i = 1; i <= n; i++)
    {
        while(dq.size()>=1 && a[dq.back()]>a[i]) dq.pop_back();
        dq.push_back(i);
        if(dq.front()==i-k) dq.pop_front();
        if(i>=k)
            ans+=a[dq.front()];
    }
    g << ans;
    return 0;
}