#include <bits/stdc++.h>

using namespace std;

#define vec vector
#define ALL(x) (x).begin(), (x).end()
#define mp make_pair
#define mt make_tuple

typedef pair< int, int > pii;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

int const inf = 1000 * 1000 * 1000;
ll const inf64 = 1ll * inf * inf;

int const N = 10005;

int n, k;
int cost[N];
ll dp[N];

bool solve() {

    for(int i = 0;i < N;i++) dp[i] = inf64;

    scanf("%d %d", &n, &k);

    for(int i = 1;i <= n;i++) {
        scanf("%d", &cost[i]);
        if(i - k <= 1) dp[i] = cost[i];
        else {
            for(int j = i - 1;j >= 1 && j + k + 1 >= i - k;j--) {
                dp[i] = min(dp[i], dp[j] + cost[i]);
            }
        }
    }

    ll res = inf64;

    for(int i = 1;i <= n;i++) {
        if(i + k >= n) {
            res = min(res, dp[i]);
        }
    }

    //printf("%lld\n", res);
    cout << res << "\n";

    return true;
}

int main() {

#ifdef MY
    while(solve());
#else
    solve();
#endif

    return 0;
}