#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> ii;

#define fill(a,x) memset(a,x,sizeof(a)) 
#define pb push_back
#define sz(x) (int)x.size() 
#define F first
#define S second
#define FOR(i,a,b) for(int i = a; i<=b; ++i)
#define NFOR(i,a,b) for(int i = a; i>=b; --i)
#define fast ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
const ll INF = 1e18;
const int mod = 1e9+7;
const int N = 1e4+10; 

int n,k;
bool cmp(ii a,ii b){
	if(a.F != b.F)return a.F < b.F;
	int l = min(a.S + k,n-1) - max(a.S - k ,0);
	int r = min(b.S + k,n-1) - max(b.S - k,0);
	return l > r;
}
ii c[N];
int a[N];
int func(int index){
	int l = max(0,index - k);
	int r = min(n-1,index + k);
	int ret = 0;
	FOR(i,l,r){
		ret += (a[i]==0);
	}
	if(ret == 0){
		return 0;
	}
	FOR(i,l,r){
		a[i] = 1;
	}
	return 1;
}
int main(){
  fast;
  cin >> n >> k;
  fill(a,0);
  FOR(i,0,n-1){cin >> c[i].F;c[i].S = i;}
  sort(c,c+n,cmp);
  ll ans = 0;
  FOR(i,0,n-1){
  	//cout << c[i].S << " ";
  	if(func(c[i].S))ans += c[i].F;
  }
  cout << ans << "\n";
  return 0;
}