#include <fstream>
#include <deque>
#define nmax 5 000 001
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
deque < int > dq;
deque < int >::iterator it;
int el, n, k, i, s, j, minn;
int main ()
{
    fin >> n >> k;

    for (i = 1; i < k; i++)
    {
        fin >> el;
        dq.push_back (el);
    }

    for (i = k; i <= n; i++)
    {
        fin >> el;
        dq.push_back (el);
        minn = 10000001;
        for (it = dq.begin (); it != dq.end (); it++)
        {
            if ((*it) < minn)
                minn = *it;
        }
        s += minn;
        dq.pop_front ();
    }

    fout << s;

    return 0;
}