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


int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll n,k;
    cin>>n>>k;
    vector<ll> a(n);
    for(int i = 0;i<n;i++) cin>>a[i];
    ll ans = 1e18;
    ll res = 0;
    priority_queue<ll> que;
    ll sum = 0;
    if(k==1){
        cout<<a[0]<<endl;
        return 0;
    }
    ll last = -1;
    for(int i = n - 1;i>=0;i--){
        if(i<k-1) break;
        ll need = (i+k-2)/(k-1);
        while(que.size()+1>need){
            sum -= que.top();
            que.pop();
        }
        if(que.size()+1==need){
            ans = min(ans,sum+a[i]);
        }
        if(need>2){
            sum += a[i];
            que.push(a[i]);
        }else if(i==n-1){
            sum += a[i];
            que.push(a[i]);
        }
    }
    cout<<ans<<endl;

}