#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e15;
int main(){
    int n,k;
    cin >> n >> k;
    vector<int> arr(n+1);
    for(int i = 1; i <= n; ++i)
        scanf("%d",&arr[i]);
    vector<ll> dp(n+1,INF);
    dp[0] = 0;
    for(int i = 1; i <= n; ++i){
        ll best = INF;
        int bid = i-1;
        for(int j = min(n,i+k); j >= max(1,i-k); --j){
            while(bid >= max(j-k-1,0)){
                best = min(best,dp[bid]);
                --bid;
            }
//            cout << "i = " << i << ", j = " << j << ": " << bid << ' ' << best << '\n';
//            cout << "touching: " << min(j+k,n) << '\n';
            dp[min(j+k,n)] = min(dp[min(j+k,n)],best+arr[j]);
            dp[min(j+k,n)] = min(dp[min(j+k,n)],dp[min(j+k+1,n)]);
        }
        for(int j = min(n,i+k)-1; j >= max(1,i-k); --j){
            dp[j] = min(dp[min(j+1,n)],best+arr[j]);
        }
//        cout << dp[i] << '\n';
    }
    cout << dp[n] << '\n';
}