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

int main()
{

    ifstream f("deque.in");
    ofstream g("deque.out");
    int n,k,sum=0;
    f>>n>>k;
    deque<int>d;
    for(int i=0;i<n;i++)
    {
        int num;
        f>>num;
        d.push_back(num);
        if(d.size()>k)
        {
            d.pop_front();
        }
        if(d.size()==k)
        {
            int min=*std::min_element(d.begin(),d.end());
            sum+=min;

        }

    }
    g<<sum;
    f.close();
    g.close();
    return 0;
}