#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> q;
int n, k, el, sum;

int main() {
    fin >> n >> k;
    for (int i = 1; i <= n; ++i) {
        fin >> el;
        if (i == 1) {
            q.push_back(el);
            continue;
        }
        for (int j = 0; j < q.size(); ++j)
            if (el < q[j])
                q[j] = el;
        q.push_back(el);
        if (i >= k) {
            sum += q[0];
            q.pop_front();
        }
    }
    fout << sum;
    return 0;
}