#include<fstream>
#include<set>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
multiset<int>heap;
multiset<int>::iterator it;
int v[5000001];
int n,k,i;
long long int sum;
int main()
{
    f>>n>>k;
    for(i=1;i<=k;i++)
    {
        f>>v[i];
        heap.insert(v[i]);
    }

    for(;i<=n;i++)
    {
        sum+=*heap.begin();
        it=heap.find(v[i-k]);
        heap.erase(it);
        f>>v[i];
        heap.insert(v[i]);
    }
    sum+=*heap.begin();
    g<<sum;
    return 0;
}