#include <fstream>
#include <deque>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
typedef long long ll;
const int N=5000005;
int v[N];
ll s;
deque <int> d;
int main()
{
    int n,k;
    in>>n>>k;
    for(int i=1;i<=n;i++)
        in>>v[i];
    in.close();
    for(int i=1;i<=n;i++){
        while(!d.empty() && v[i]<=v[d.back()])
            d.pop_back();
        d.push_back(i);
        if(d.front()==i-k)
            d.pop_front();
        if(i>=k)
            s+=v[d.front()];
    }
    out<<s<<"\n";
    out.close();
    return 0;
}