#include <iostream>
#include <fstream>

using namespace std;

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

int n, a[5000001], v[5000001], k, st, dr;
long long s;

int main()
{
    in >> n >> k;
    st=1;
    dr=0;
    for (int i=1; i<=n; i++)
    {
        in >> a[i];
        if (st <= dr && v[st] == i-k)
        {
            st++;
        }
        while (st <= dr && a[v[dr]] >= a[i])
        {
            dr--;
        }
        v[++dr] = i;
        if (i > k-1)
            s = s + a[v[st]];
    }
    out << s;
    return 0;
}