#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

typedef long long ll;

const ll INF = (1LL << 50);

int main() {
    int n, k;
    scanf("%d%d", &n, &k);
    vector <int> a(n);
    for (int i = 0; i < n; ++i) {
        scanf("%d", &a[i]);
    }
    vector <ll> dp1(n);
    vector <ll> dp2(n);
    for (int i = 0; i < n; ++i) {
        ll curDp;
        if (i <= k) {
            curDp = 0;
        } else {
            curDp = INF;
            for (int j = 2 * k + 1; j <= i && j <= 2 * k + 1; ++j) {
                curDp = min(curDp, dp1[i - j]);
            }
        }
        dp1[i] = curDp + a[i];
        //dp1[i] = a[i] + (i <= k ? 0 : dp2[i - k - 1]);
        dp2[i] = INF;
        for (int j = 0; j <= k && j <= i; ++j) {
            dp2[i] = min(dp2[i], dp1[i - j]);
        }
    }
    printf("%lld\n", dp2[n - 1]);
    return 0;
}