#pragma region Header
#include <climits>
#include <map>
#include <queue>
#include <iomanip>
#include <cstdlib>
#include <functional> 
#include <unordered_map>
#include <unordered_set>
#include <stdio.h>
#include <ctime>
#include <stack>
#include <sstream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>
#include <set>
#include <iostream>
#include <cassert>

#define ft first
#define sc second

#define X first
#define Y second

#define mp make_pair

#define All(x) (x).begin(),(x).end()
#define rAll(x) (x).rbegin(),(x).rend()
typedef long long ll;
typedef long double ld;
using namespace std;

ld PI = acos(-1);

template<class T>inline const T sqr(const T & x) { return x*x; }
ll popcnt(ll mask) { ll cnt = 0; while (mask) cnt += mask & 1, mask >>= 1; return cnt; }
ll powi(ll a, ll b, ll mod = 1000000007) { if (b < 2) return b ? a : 1; return (powi((a*a) % mod, b / 2, mod)*(b % 2 ? a : 1LL)) % mod; }
ll mod7 = 1000000007; ll mod9 = 1000000009;
bool isprime(ll n) { if (n < 2) return 0; for (ll i = 2; i*i <= n; i++) if (n%i == 0) return 0; return 1; }
#pragma endregion

int main()
{
	ios::sync_with_stdio(0);
	int n, k; cin >> n >> k;
	vector<ll> a(n); 
	for (int i = 0; i < n; i++) cin >> a[i];
	vector<ll> dp(n + k, 1e16);
	for(int i = k; i < n+k;i++)
	{
		for (int j = max(-1, i - k * 2 - 1); j < i; j++)
			dp[i] = min(dp[i], (j==-1?0:dp[j]) + a[i - k]);
	}
	ll ans = 1e16;
	for (int i = n - 1; i < n + k; i++) ans = min(ans, dp[i]);
	cout << ans << endl;
#ifdef _DEBUG
	system("pause");
	//	cin.get(); cin.get();
#endif
	return 0;
}