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

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

deque<int>h;
int v[5000001];
int main()
{
    int n, k, i;
    long long suma=0;
    fin>>n>>k;
    for(i=1; i<=n; i++)fin>>v[i];

    for(i=1; i<=n; i++)
    {
        while(!h.empty() && v[i]<=v[h.back()]) h.pop_back();
        h.push_back(i);
        if(h.front()==i-k) h.pop_front();
        if(i>=k) suma+=v[h.front()];
    }
    fout<<suma;
}