#include <bits/stdc++.h>
using namespace std;
map <int ,long long int > m;
long long int solve(int a[],int i,int n,int k){
    //cout<<"*"<<i<<endl;
    if(i>=n){
        return 0;
    }
    if(m.find(i) != m.end() )return m[i];
    long long int mini=999999999;
    for(int ii=i;ii<=i+k && ii<n;++ii){
        long long int x=solve(a,ii+k+1,n,k)+a[ii];
       // x=a[k+1-ii];
        //cout<<"::"<<endl;
        //cout<<ii<<" " <<x<<endl;
        mini=mini<x?mini:x;
        //cout<<mini<<" ";
        //if()
    }
   /// cout<<i<<" "<<mini<<endl; 
    m[i]=mini;
    return mini;
    
}
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    int n,k;
    cin>>n>>k;
    int a[n+5];
    for(int i=0;i<n;++i){
        cin>>a[i];
    }
    m.clear();
    long long int ans=solve(a,0,n,k);
    cout<<ans<<endl;
    return 0;
}