#include <fstream>
#include <deque>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
deque <int> d;
int i, n, k, a[5000000]; long long sol=0;
int main()
{
    in>>n>>k;
    for(i=1;i<=n;i++)
        in>>a[i];
    for(i=1;i<=n;i++)
    {
        while(!d.empty() && a[i]<a[d.back()])
            d.pop_back();
        d.push_back(i);
        if(d.front()==i-k)
            d.pop_front();
        if(i>=k) sol+= a[d.front()];
    }
    out<<sol;
    return 0;
}