#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

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

const int N = 5e6+5;
int n, i, k;
long long rez;
int v[N];

deque <int> mi;

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

    for(i = 1; i <= n; i++){
        while(!mi.empty() && v[i] <= v[mi.back()])
            mi.pop_back();
        mi.push_back(i);

        while(!mi.empty() && i - mi.front() >= k)
            mi.pop_front();

        if(i >= k) rez += v[mi.front()];
    }
    fout << rez;
    return 0;
}