#include <bits/stdc++.h>
using namespace std;
#define doi pair<int, int>
#define cost first
#define poz second
ifstream f("deque.in");
ofstream g("deque.out");
int n, k, x;
long long rez;
priority_queue <doi, vector<doi>, greater<doi>> pq;

int main()
{
    f >> n >> k;
    for(int i=1; i<=k; i++)
        f >> x, pq.push(make_pair(x, i));
    rez+=pq.top().cost;
    for(int i=k+1; i<=n; i++)
    {
        f >>x;
        pq.push(make_pair(x, i));
        while(pq.top().poz <= i-k)
            pq.pop();
        rez += pq.top().cost;
    }
    g << rez;
}