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

#define MOD 1000000007
#define pb push_back
#define mp make_pair
#define all(c) (c).begin(),(c).end()
#define sz(a) int((a).size())
#define F first
#define S second

#define rep(i, a, b) for(int i = a; i < b; ++i)
#define per(i, a, b) for(int i = a; i >= b; --i)
#define travel(c,itr) for(__typeof((c).begin()) itr=(c).begin();itr!=(c).end();itr++)
#define INDEX(arr,ind)			(lower_bound(all(arr),ind)-arr.begin())

typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef pair<ll,int> pli;
typedef pair<ll,ll> pll;
typedef pair<int, pii> piii;
typedef pair<ll, pll> plll;
typedef vector<pii> vpii;
typedef vector<piii> vpiii;

inline ll powmod(ll x, ll n, ll _mod){ 
  ll res = 1; 
  while (n){
    if (n & 1)res = (res*x) % _mod; 
    x = (x*x) % _mod; 
    n >>= 1;
    }
    return res; 
  }


#define N 10005
int n,k;
int c[N];
const ll inf = 1e16;

map<pii,ll> memo;

ll sol(int pre,int cur,ll cost=0){ //cout<<pre<<" "<<cur<<" "<<cost<<endl;
int x1=pre+k;
int x2=cur-k;
	if((x2-x1)>1)return inf;
	if(cur>n){
		if(x1>=n)return memo[mp(pre,cur)]=cost;
		return inf;
	}
	if(memo.count(mp(pre,cur)))return memo[mp(pre,cur)];
	ll ret=inf;
	ret=sol(cur,cur+k,cost+c[cur]);
	ret=min(ret,sol(pre,cur+1,cost));
	return memo[mp(pre,cur)]=ret;
}

int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

// freopen("in.txt","r",stdin);
// freopen("o.txt","w",stdout);

cin>>n>>k;
ll sum=0;
for(int i=1;i<=n;i++){
	cin>>c[i];
	sum+=c[i];
}

if(k==0){
	cout<<sum<<'\n'; return 0;
}

ll ans=sol(1-k-2,1);
cout<<ans<<'\n';
return 0;
}