#include <fstream>
#include <deque>

using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");

int n, k, a[5000005];
long long sum;
deque<int> dq;

int main()
{
    cin>>n>>k;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    for(int i=1;i<=n;i++){
        while(dq.size()>0&&a[dq.back()]>=a[i]){
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front()==i-k){
            dq.pop_front();
        }
        if(i>=k){
            sum+=a[dq.front()];
        }
    }
    cout<<sum;
    return 0;
}