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