#include <fstream>
#include <deque>
 
using namespace std;
 
ifstream f("deque.in");
ofstream g("deque.out");
deque <int> d;
int v[5000001],i,n,k;
long long s;
int main()
{
    f>>n>>k;
    for(int i=1;i<=n;i++)
        f>>v[i];
    for(int i=1;i<=n;i++)
    {
        while(!(d.empty()) && v[i]<=v[d.back()])
            d.pop_back();
        d.push_back(i);
        if(i-k == d.front())
            d.pop_front();
        if(i>=k)
            s=s+v[d.front()];
    }
    g<<s;
    return 0;
}