#include <fstream>
#include <deque>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n, k, a[100005], i, ans;
deque <int> q;
int main()
{
    fin>>n>>k;
    for(i=1; i<=n; i++)
        fin>>a[i];
    q.push_back(1);
    for(i=2; i<=k; i++)
    {
        while(!q.empty() && a[q.front()]>=a[i])
            q.pop_front();
        q.push_front(i);
    }
    ans=a[q.back()];
    for(i=1; i<=n-k; i++)
    {
        if(q.back()==i)
            q.pop_back();
        while(!q.empty() && a[q.front()]>=a[i+k])
            q.pop_front();
        q.push_front(i+k);
        ans+=a[q.back()];
    }
    fout<<ans;
    return 0;
}