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

typedef unsigned long long ull;

ull dp[1000];
ull c[1000];

int main() {
    int n, k;
    cin >> n >> k;
    for(int i = 0; i < n; ++i) {
        cin >> c[i];
        dp[i] = c[i] + (i-k-1 >= 0 ? dp[i-k-1] : 0);
        for(int j = i-1; j >= i-k && j >= 0; --j) {
            dp[i] = min(dp[i], c[j] + (j-k-1 >= 0 ? dp[j-k-1] : 0));
        }
    }
    cout << dp[n-1] << endl;
    return 0;
}