#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pdd pair<double,double>
#define FILL(a,x) memset(a,x,sizeof(a))
#define foreach( gg,ii ) for( typeof(gg.begin()) ii=gg.begin();ii!=gg.end();ii++)
#define mp make_pair
#define pb push_back
#define X first
#define Y second
#define sz(a) int((a).size())
#define N 10010
#define MAX 30
#define mod 1000000007
#define REP(i,a) for(int i=0;i<a;++i)
#define REPP(i,a,b) for(int i=a;i<b;++i)
#define all(a) a.begin(),a.end()
const ll INF = 1e18+1;

ll c[N],dp[N];
int n,k;

ll solve(int idx)
{
	if (dp[idx]!=INF) return dp[idx];
	ll ans=INF;
	REPP(i,idx,min(idx+k+1,n))
	{
		if (i+k+1<n) ans=min(ans,c[i]+solve(i+k+1));
		else ans=min(ans,c[i]);
	}
	dp[idx]=ans;
	return ans;
}

int main()
{
	scanf("%d%d",&n,&k);
	REP(i,n) scanf("%lld",&c[i]);
	REP(i,n) dp[i]=INF;
	printf("%lld\n",solve(0));
return 0;
}