#include <iostream>
#include <fstream>
#include <algorithm>
#include <cstdio>
#include <string>
#include <string.h>
#include <vector>
#include <queue>
#include <deque>

using namespace std;

ofstream out("deque.out");

int n,k,sum;
vector<int> v;
deque<int> deq;

int main()
{
    freopen("deque.in", "r", stdin);
    scanf("%d %d ", &n, &k);
    v=vector<int>(n+1);
    for(int i=1; i<=n; i++)
    {
        int x;
        scanf("%d ", &x);
        v[i]=x;
    }
    deq.push_back(1);
    for(int i=2; i<=n; i++)
    {
        int x=deq.back(),y=deq.front();
        while(deq.begin()!=deq.end() and v[i]<=v[deq.back()]) deq.pop_back();
        deq.push_back(i);
        if(deq.front()==i-k) deq.pop_front();
        if(i>=k) sum+=v[deq.front()];
    }
    out<<sum;
    return 0;
}