#include <iostream>
#include <fstream>
#include <queue>
using namespace std;
const int dim=5e6+5;
int n,a[dim],k;
deque<int> dq;
long long s;
signed main(){
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    cin>>n>>k;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    for(int i=1;i<=n;i++){
        while(!dq.empty() and a[i]<=a[dq.back()]){
            dq.pop_back();
        }
        dq.push_back(i);
        if(i>=k){
            while(!dq.empty() and dq.front()<=i-k){
                dq.pop_front();
            }
            s+=a[dq.front()];
        }
    }
    cout<<s;
    return 0;
}