/*
ye mera template hai
apna khud likho bc :P
*/

/*
Author : Sarvagya Agarwal
*/

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

//defines
#define openin freopen("input.txt","r",stdin)
#define openout freopen("output.txt","w",stdout)
#define fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define ll long long
#define int long long
#define mod 1000000007
#define rep(i,x,y) for (__typeof(x) i=x;i<=y;i++)
#define all(c) (c).begin(),(c).end()
#define ff first
#define ss second
#define pb push_back
#define mp make_pair

int power(int a , int b)
{
    int res = 1 ;
    while(b)
    {
        if(b%2) {
            res = (res * a)%mod ;
        }
        b/=2 ;
        a = (a*a)%mod ;
    }
    return res ;
}

//debug
#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
int n , k ;
const int inf = 1e18 ;
int dp[10005][2] , dp2[10005][2] ,arr[10005] ;
int32_t main()
{
    fast;
    cin >> n >> k ;
    rep(i,1,n)cin >> arr[i] ;
    dp[0][0] = dp[0][1] = 0 ;
    for(int i = 1 ; i <= n ;++i) {
        int min_cost = inf ;
        for(int j = max(1ll,i-k) ; j < i ; ++j) {
            min_cost = min(min_cost,dp[j][1]) ;
        }
        dp[i][0] = min_cost ;
        dp[i][1] = arr[i] ;
        if(i-k > 1ll) {
            dp[i][1] += min(dp[i-k-1][0],dp[i-k-1][1]) ;
        }
    }
    dp2[n+1][0] = dp2[n+1][1] = 0 ;
    for(int i = n ; i >= 1 ;--i)
    {
        int min_cost = inf ;
        for(int j = i + 1 ; j <= min(i+k,n);++j) {
            min_cost = min(min_cost,dp2[j][1]) ;
        }
        dp2[i][0] = min_cost ;
        dp2[i][1] = arr[i] ;
        if(i+k < n) {
            dp2[i][1] += min(dp2[i+k+1][0],dp2[i+k+1][1]) ;
        }
    }
    int ans = inf ;
    for(int i = 1 ; i <= n ; ++i) {
        int cost = arr[i] ;
        if(i-k > 1)cost += min(dp[i-k-1][0],dp[i-k-1][1]) ;
        if(i+k < n)cost += min(dp2[i+k+1][0],dp2[i+k+1][1]) ;
        ans = min(ans,cost) ;
    }
    cout << ans << endl;
    return 0;
}