#include <iostream>
#include <cstdio>
#include <bitset>
#include <vector>
#include <numeric>
#include <string>
#include <algorithm>
#include <map>
#include <cmath>
#include <climits>
#include <set>
#include <queue>
#include <stack>
#include <cstring>
#include <ctime>
#include <cstdlib>
#include <cassert>

using namespace std;

#define mem(a, v) memset(a, v, sizeof (a))
#define x first
#define y second
#define all(a) (a).begin(), (a).end()
#define mp make_pair
#define mt make_tuple
#define sz(x) int((x).size())
#define rep(i, n) for (int i = 0; i < int(n); i ++)
#define repi(i, a, n) for (int i = (a); i < int(n); i ++)
#define repe(x, v) for (auto x: (v))
#define vt(x) vector < x >
#define px(x) pair < x, x >
#define pxy(x, y) pair < x, y >

typedef long long ll;

int main () {
  std::ios_base::sync_with_stdio(false);
  int n, k;
  cin >> n >> k;
  vt(ll) c(n), dp(n+1);
  repe(&e, c) {
    cin >> e;
  }
  for (int i = n-1; i >= 0; i --) {
    dp[i] = LLONG_MAX;
    repi(j, i, min(i+k+1, n)) {
      dp[i] = min(dp[i], dp[min(j+k+1, n)] + c[j]);
    }
  }
  cout << dp[0] << endl;
  return 0;
}