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

#define LL long long
#define F first
#define S second
#define MP make_pair
#define PB push_back
#define SZ(a) (int)(a.size())
#define BS(vec,val) (int)(lower_bound(vec.begin(),vec.end(),val) - vec.begin())
#define bitcount __builtin_popcountll
#define LET(it,container) __typeof(container.begin()) it(container.begin())
#define ITER(it,container) for(__typeof(container.begin()) it=container.begin();it!=container.end();it++)

#define PREC cout << setprecision(10) << fixed;
#define FIO ios_base::sync_with_stdio(0); cin.tie(NULL);
#define DB(x) cerr << #x << ": " << x << " ";
//-std=c++11
//#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
	cerr << name << " : " << arg1 << std::endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
	const char* comma = strchr(names + 1, ',');cerr.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
}
#else
#define trace(...)
#endif
//FILE *fin = freopen("in","r",stdin);
//FILE *fout = freopen("out","w",stdout);
#define endl "\n"

const double PI = acos(-1.0);
const int MOD = 1e9 + 7;
const LL INF = 1e15 + 9;
const int MX = 1e4 + 5;

int n,k;
LL inp[MX];
LL dp[MX];

LL solve(int idx)
{
	if(idx > n)
		return 0;
	if(dp[idx] != -1)
		return dp[idx];
	LL ret = INF;
	int cnt = 0;
	for(int i=idx;i<=n;i++)
	{
		if(cnt > k) break;
		ret = min(ret,solve(i+k+1) + inp[i]);
		cnt++;
	}
	return dp[idx] = ret;
}

int main()
{
	FIO;
	cin >> n;
	cin >> k;
	for(int i=1;i<=n;i++)
		cin >> inp[i];

	memset(dp,-1,sizeof dp);
	cout << solve(1) << endl;	

	return 0;
}