#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k;
int a[5000006];
deque <int> d;
int main()
{
    int i;
    long long sum=0,x;
    fin >> n >> k;
    for (i=1; i<=n; i++)
        fin >> a[i];
    for (i=1; i<=n; i++)
    {
        x=a[i];
    while (!d.empty() and a[d.back()]>=x)
    d.pop_back();
    d.push_back(i);
    if (d.front()<=i-k) d.pop_front();
    if (i>=k) sum+=a[d.front()];
    }
    fout << sum;


    return 0;
}