#include <bits/stdc++.h>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
const int nm=5e6+5;
int a[nm];
deque <int> d;
int n,k;
long long sum;
int32_t main()
{
    f>>n>>k;
    for(int i=1; i<=n; i++)
        f>>a[i];
    d.push_back(1);
    for(int i=2; i<=n; i++)
    {
        while(d.front()<=d.back() && a[d.back()]>=a[i])
            d.pop_back();


        d.push_back(i);
        if(d.front() ==i-k)
            d.pop_front();
        if(i>=k)
            sum+=a[d.front()];

    }
    g<<sum;
    return 0;
}