#include <fstream>
#include<deque>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
int n,k;
int arr[50001];
deque<int> dq;
int main()
{
    in>>n>>k;
    for(int i=1; i<=n; i++)
    {
        in>>arr[i];
    }
    long long ans=0;
    for(int i=1; i<=n; i++)
    {
        while(!dq.empty() && arr[dq.back()] >= arr[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front()==i-k)
        {
            dq.pop_front();
        }
        if(i>=k)
        {
            ans+=arr[dq.front()];
        }
    }
    out<<ans;
    return 0;
}