#include <fstream>
#include <deque>
#include <iostream>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

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

int main()
{
    f>>n>>k;
    for(int i=1; i<=n; i++)
    {
        f>>a[i];
    }
    for(int i=1; i<=n; i++)
    {

        while(!dq.empty() && a[dq.back()]>=a[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(i-k==dq.front())
        {
            dq.pop_front();
        }
        if(i>=k)
            s+=a[dq.front()];
    }
    g<<s;
    return 0;
}