#include <fstream>
#include<deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque <int> d;
int n,k,s,v[5000010],i,u,p;
int main()

{
    f>>n>>k;
    for(i=1;i<=n;i++)
        f>>v[i];
    for(i=1; i<=n; i++)
    {
        while(!d.empty()&&v[i]<v[d[d.size()-1]])
             d.pop_back();
            d.push_back(i);
            if(d[0]==i-k)
                d.pop_front();
            if(i>=k)
                s+=v[d[0]];
    }
    g<<s;
}