#include <iostream>
#include <fstream>
#include <deque>
#include <vector>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> D;
vector <int> a;
int n,k;
int sum;
void citire()
{
    fin>>n>>k;
    a.resize(n+1);
    for(int i=1;i<=n;i++)
    {
        fin>>a[i];
        while(!D.empty() && i-D.front()>=k)
          D.pop_front();
        while(!D.empty() && a[i]<a[D.back()])
          D.pop_back();
        D.push_back(i);
        if(i>=k)
        {
            sum=sum+a[D.front()];
        }
    }
    fout<<sum;
}
int main()
{
    citire();
    return 0;
}