/******************************************************************************

                              Online C++ Compiler.
               Code, Compile, Run and Debug C++ program online.
Write your code in this editor and press "Run" button to compile and execute it.

*******************************************************************************/

#include <fstream>
#include <deque>
using namespace std;
int n,k,v[500001];
long long sum=0;
ifstream cin("deque.in");
ofstream cout("deque.out");
int main()
{
    cin>>n>>k;
    for(int i=1;i<=n;i++)
    {
        cin>>v[i];
    }
    deque <int>dq;
    for(int i=1;i<=n;i++)
    {
        if(!dq.empty() && dq.front()<i-k+1)
        {
            dq.pop_front();
        }
        while(!dq.empty() && v[dq.back()]>=v[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(i>=k)
        {
            sum += v[dq.front()];
        }
    }
    cout<<sum;
    return 0;
}