#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,deq[5000010],fr,bk;
long long sum;
vector<int> v;

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;
    }
    fr=1,bk=0;
    for(int i=1; i<=n; i++)
    {
        while(fr<=bk and v[i]<=v[deq[bk]]) bk--;
        deq[++bk]=i;
        if(deq[fr]==i-k) fr++;
        if(i>=k) sum+=v[deq[fr]];
    }
    out<<sum;
    return 0;
}