#include <bits/stdc++.h>

using namespace std;

deque <int> d;

int n, x, a[100005], k, nr, s, h;

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

int main()
{
    f >> n >> k;
    for(int i=1; i<=n; i++)
    {
        f >> x;
        if(nr==k) d.push_front(x), nr=0, d.pop_back();
        else
        {
            if(!d.empty())
            {
                while(d.front()>=x) {
                        d.pop_front();
                        h=d.front();
                }
            }
            d.push_front(x);
            nr++;
        }
        h=d.front();
        if(i>=k)s+=d.back();
    }
    g << s;
}