#include <bits/stdc++.h>
#include <algorithm>

#define pb push_back
#define mp make_pair
#define mt make_tuple
#define ll long long
#define pii pair<int,int>
#define tii tuple <int,int,int>
#define N 1000005
#define mod 100000000000000000
#define X first
#define Y second
#define eps 0.0000000001
#define all(x) x.begin(),x.end()
#define tot(x) x+1,x+n+1
using namespace std;
ll sol,dp[N],a[N],sc,i,j,n,k;
int main()
{
    cin.sync_with_stdio(0);
    cout.sync_with_stdio(0);
    cin>>n>>k;
    for(i=1; i<=n; i++)
    {
        cin>>a[i];
        dp[i]=mod;
    }
    for(i=1; i<=n; i++)
    {
        sc=0;
        for(j=i-1; j>=0&&j>=i-k; j--)
            sc=min(sc,a[j]);
        dp[i]=min(dp[i],sc+a[i]);
    }
    sol=mod;
    for(j=n; j>=0&&j>=n-k; j--)
        sol=min(sol,dp[j]);
    cout<<sol;
    return 0;
}