#include <bits/stdc++.h>
using namespace std;
int cost[10010];

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    int n,k;
    cin>>n>>k;
    
   int i,j;
   
    for(i=0;i<n;i++)
        cin>>cost[i];
    
    
    long long ans=0;
    
    for(i=0;i<n;i++)
        {
        int tmp=INT_MAX;
        int idx;
        
        for(int j=0;j<n;j++)
            {
            if(cost[j]<tmp)
                {
                tmp=cost[j];
                idx=j;
            }
            
                
        }
        
          if(tmp==INT_MAX)
              break;
        
           ans+=cost[idx];
        int oo=min(idx+k,n-1);
        
          for(int j=max(idx-k,0);j<=oo;j++)
              cost[j]=INT_MAX;
        
             
    }
    
    
    cout<<ans;
    
    return 0;
}