#include <bits/stdc++.h>
using namespace std;
#define ll long long
ll cost[10001];
ll k;

ll solve(ll st,ll en){
    ll i;
    ll ans=1e18;
    for(i=st;i<=en;i++){
        ll val=0;
        val+=cost[i];
        ll l=i-k-1,st;
        ll r=i+k+1;
        if(l>=st)
            val+=solve(st,l);
        if(r<=en)
            val+=(r,en);
        ans=min(val,ans);
    }
return ans;
}

int main(){
    ll n;cin>>n>>k;
    ll i;
    for(i=0;i<n;i++)
        cin>>cost[i];
    cout<<solve(0,n-1);
}