#include<iostream>
#include<bits/stdc++.h>
#include<fstream>
using namespace std;

#define NMAX 5000005

ifstream fin("deque.in");
ofstream fout("deque.out");

deque<int> d;

int v[NMAX];

int main()
{
    long long s = 0;
    int n,k;
    fin>>n>>k;

    for(int i=1;i<=n;i++)
        fin>>v[i];

    for(int i=1;i<=n;i++)
    {

        while(!d.empty() && v[d.back()] >=v[i])
        {

            d.pop_back();
        }
        d.push_back(i);

        if(d.front() == i-k)
            d.pop_front();

        if(i>=k)
            s+=v[d.front()];

    }
    fout<<s;
    return 0;
}